Thanks Lin Alan - I guess a better explanation is that it became a dumb trainer but still reported power and cadence.
Correct me (anybody), if I’m wrong, but I think smart trainer (and NEO is smart one) is connected in TWO independent/separate ways to Zwift:
- Power source - trainer reports/sends Watts to software, so Zwift knows the power you produce …
- Controllable - trainer GETS information from Zwift (gradient info) so it can react and change its resistance according to terrain simulation.
These two connections are independent, even mostly they are established/linked automatically in one moment.
But if Controllable connection is lost (for whatever reason) or Zwift controllable channel is connected to something else than your trainer (for whatever reason again) , then trainer still reports power = you can see your watts, but the trainer doesn’t get info from Zwift = thus doesn’t respond to simulation of terrain = change of gradient doesn’t affect change of trainer resistance.
Check (in Pair screen) if your trainer is listed in both - Power + Controllable.
I hope my poor English is good enough and you will understand what I mean … 
Nowadays zwift is going crazy!
Hi Godmother Fox, when I looked into this it appears the Neo just uses one BLE channel for everything. I use an AppleTV 4K that only has only has 2 spare BLE channels, and one is used for the Neo and the other for my TickR heart rate monitor.
Yes, You are right … if everything works as intended, then both - watt+controllable should be transmitted together via one BLE channel … my post was just “long shot” - if your pairing screen says Tacx Neo for both, then the problem is somewhere else …
Your post above is correct regarding power and controllable trainer.
Also, you can get cadence, power, and controllable trainer in one BLE connection if all are the NEO. However, many users will use their own power source (e.g., Quarq, p2max, Stages, etc…). As a result, the NEO will be one BLE connection and the power will be another BLE connection. So you will have to pair the HRM thru the Companion app.
@Bannister99 Are you using an separate power source?
Hi Lin, no just the Neo for power, cadence and resistance. Perhaps it was just a one off - There were literally thousands taking part in this Zwift TDZ stage 2 race.
Well it wasn’t a one off - Just done it again but this time on a free ride 
I might as well throw my issue on this pile. I’ve been riding Zwift for a little over a year now, and a Tacx Neo 1 since May 2018. Things worked as expected until January 2019, when randomly, Zwift would stop controlling the resistance on the Neo, or the resistance changes seemed delayed by some number of minutes.
Yesterday this happened riding the Knickerbocker loop, 1/3 of they way up the KOM Arch. Resistance dropped to nearly nothing, where a few moments earlier it had matched the 13% grade the game was presenting. Speed was adjusted for the lowered wattage, and the avatar was displaying a matching cadence, so the bluetooth connection wasn’t lost completely. About 20 minutes later, I got fed up with it, and rebooted the neo, and unpaired/repaired it, and continued the ride. Resistance control was back, and when it did the KOM arch the second time, resistance matched the displayed grade the whole way.
I looked over the log, and I could see where the Neo repaired later in the ride, but no obvious errors when the resistance control went away.
My setup is a macbook pro, just using BTLE. No ANT dongle. I verified I wasn’t in ERG mode, or doing a training program. My ride type was “Just Ride”. I haven’t changed the distance between or locations of, the macbook, or the Neo. I checked and there are no updates pending for the Neo, and none have been installed since it was initially set up in May 2018.