Zwift Companion app on iOS16 won't connect [September 2022] [SOLVED]

I’ve had problems with the companion app connected to the Zwift app for years on my mesh network and I’ve run wireshark to see if I could figure out what’s going on.

From what I can tell, Zwift is mishandling something related to a failed TCP/IP handshake. I think what happens is the ACK gets corrupted, and somehow one end (the desktop app, IIRC) thinks the connection has been made, but the phone thinks it has failed and starts trying to establish a new connection on the same port, which is causing an error, and the timeout for the error is something like 5 minutes. (I don’t have this exactly right, but its along these lines, I’d have to go find the packets again).

For me this happens on my mesh network if my phone is connected to one of the APs that is further away from my Zwift setup (this happens, if, for instance, I am using the internet upstairs before Zwifting and then walk down to the basement, the phone won’t immediately jump to the closer AP). Since the AP my phone is talking to is farther away, the chance of a corrupted packet during the handshake is larger (it’s also going through a lot of plumbing between the basement and the upstairs). If instead I turn off my wifi completely on the phone for a minute before going downstairs (in the settings, not in the quick menu–the iPhone only suspends the connection and doesn’t fully power it down if you don’t do it in the settings app), then I start Zwift downstairs, then turn on the phone’s wifi, which automatically connects to the same AP as the Zwift computer, and then start the companion app–I have no problems. But if I start in the other room, I can get the failed TCP/IP handshake error packets between Zwift and the companion app as the companion app tries desperately to connect and Zwift keeps replying it has already reserved that port.

In case someone wants to look into this the error is (as shown in Wireshark):

[TCP Retransmission] [TCP Port numbers reused] 49384 → 21587 [SYN] …

and I just get the error over and over again. It looks like the source is the laptop and the destination is the phone.

In my packet capture. No handshake is initiated from either my phone nor Zwift.

In my case, an iPhone 13 Mini is also affected, and there were other users having the issue with 13 Mini, too, here in the thread (but it became a bit too long to find them).

Same problem here with new iPhone 14 Pro Max with iOS 16.4
Same laptop + wifi + another iPhone 12 with iOS 16.4 works fine.

Hello everyone,

We have some new information and I want to give another update to help clarify the issue.

  • First, welcome to all the first-time forum visitors! I’m sorry it ended up being this circumstance that brought you here.

  • If you haven’t contacted me in Community Support, I still recommend doing so. Either we’ll be able to help your ZC reconnect, or I’ll be able to make sure that your device information and configuration is tracked properly. If your iOS device has ever connected ZC to Zwift, then it’s likely that we’ll be able to help you get your connection re-established

  • This issue is affecting a small number of Zwifters who use ZC an iOS device running iOS16, where Zwift Companion is unable to connect to Zwift.

    • It is not affecting all devices running iOS16
    • It is not affecting only iPhone 14 models
    • It is not directly related to the Local Network permissions toggle
  • While we still have not been able to reproduce this internally, we do have a more clear picture on the root cause which has enabled us to start working on a resolution. I will continue to give more updates as testing on this progresses.


Thanks Rowdy, pls keep me in the loop. Used iP13m with no probs for nearly two years. Recently moved to iP14P, never managed to connect. Looking forward…

Rowdy, my ZC app on the iPhone 14 still can’t connect to Zwift. Here are the specifics of the device configuration I am using:

  • ZC app is installed on iPhone 14 Pro Max running IOS 16.4.1 (already had and reported the issue on 3/24 when running IOS 16.4)
  • ZC app does NOT load the map of the road I intend to/rode. ZC app DOES show in the “Activities” the course I was going to ride/metric of the course I rode
  • Zwift app (version 1.33.6 (109384) is running on Apple TV OS 16.4
  • ZC app running on iPad OS16.4 is working fine (I can’t used it when riding as I do not have the appropriate support/place to safely hold the iPad while riding)
    Please contact me at if you have any questions and/or need further information.
    Thank you in advance for your help.

So I read all of this as saying that whatever the secret root cause is, there’s nothing a consumer can do and the fix will have to come from Zwift?
It’s not all devices though, so is it therefore possible that the simple action of returning one’s phone to the store for a different color would do the trick?

Or can you specify yet which phone models we should avoid purchasing if that’s possible?

Or, Is it possible with whatever you know that once the next version (16.5?) of iOS is out, the problem might go away?

According to an email I received from Zwift, here’s my understanding of the situation:

You may or may not be aware, but the screen of your iPhone could be manufactured by either LG or Samsung.

I speculate that a similar scenario might apply to the networking components of iPhones.

It appears that Apple has some inconsistencies in their manufacturing process, while Zwift, on the other hand, overlooked this issue and is now trying to catch up and save face.

Regarding your questions, my understanding is affirmative for both. If you exchange your iPhone, the next one might be compatible with Zwift, and if you keep your current phone, it will likely start working with an upcoming companion release (not iOS), based on the explanation provided by Zwift for the occurrence of this issue.

Using multiple suppliers/manufacturers to diversify the supply chain as well as increased capacity/supply is not some inconsistency in the manufacturing process. It’s also quite normal.

Are you here to discuss the nuances of terminology? According to the email from Zwift, Apple shares some responsibility for the issues with the Companion app, as well as a number of other iPhone applications I use, such as Sony Creators’.

I have been involved in some of the testing to identify the problem. Without speaking out of turn (as a software dev), some assumptions have been made in coding the Zwift companion app and as a result, the interface on which the iPhone communicates on wifi may not be always what is assumed. Personally, the issue is not Apples fault, but laziness from the developers. In saying that, I’m glad we might be closer to have the issue fixed for us all

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I have an iPhone 12. Companion just stopped working-no map, but everything else. Nothing in my set up has changed-for over 2 years. Suddenly, past week the map is not there. So, just saying it is not isolated to IP14.
Never heard of Trainer road, but may cancel and try.

Zwift requested my assistance in testing a solution to address a network interface problem too. While it’s true that assumptions should not have been made and that there might be a more adaptable approach to coding the app, the inconsistency in Apple’s network interface changes for one device and not the others, as previously mentioned, likely contributed to this issue.

Determining whether Apple shares responsibility is difficult without being a Swift developer. Nonetheless, I have observed other apps impacted by this situation. Just to clarify, the programming languages used are Swift or Objective-C.

Pardon if this has already been posted by someone else, but here my findings so far…I noticed a difference in the Bluetooth feature in my old phone, and not available on the new one. inside the Companion Settings.

Old iPhone 8, iOS 14.1 version, Apple TV

iPhone 8 About
Companion Settings

New Phone is an iPhone 14 Pro, 16.4.1 iOS version

New Phone Companion Settings
New iPhone About

We’re having this same problem all of the sudden. Our ZC connection had been working perfectly until last week when it suddenly didn’t. We changed our iPhones in late December and it’s only now that we have an issue.
My phone:
iPhone 14
IOS vision 16.3.1
ZC 1.319.0

Her phone:
iPhone 14 Pro
IOS vision 16.3.1 when problem started
IOS vision 16.4.1 after update yesterday
ZC 1.319.0

And, because I use ZC for heart rate too, that’s also unavailable.

Does anyone really have any ideas what the problem is? This is now month 4 of the same problem. Any chance that new Zwift update might solve this? If so, can you push it out faster?

I have always found the ZC Apple connection a bit iffy especially with iWatch having to reboot my phone frequently to get the iWatch connection working. But at least it was working.



Your issue sounds different… You’ve been running the same iphone since December and only now the issue arose? Were you on ios 15.x or somesuch up until last week?

The problem has been since I switched to the new phone back in February…

Hi @John_Carnes , if your phone has connected ZC to Zwift, then I don’t believe that you’re experiencing the main issue on this Forum thread. It’s most likely that some troubleshooting can help get you reconnected. Feel free to dm me or open up a support ticket if this issue persists for you.