I run Zwift on a Windows PC, so I use the app formerly known as ZML on my iPhone to provide Bluetooth connectivity for my sensors. (Don’t get me started on the lack of native Bluetooth support on Windows.)
Lately, I’ve found that Zwift often doesn’t see the Tickr-X, even though my iPhone shows it as a connected Bluetooth device. I’ve killed all of the other apps on the iPhone and turned the iPhone’s Bluetooth off and on again, to no avail. The iPhone always reports the Tickr-X as a connected Bluetooth device, but Zwift refuses to acknowledge its presence.
It seems that this started happening around the time of the last Zwift update, but I can’t say for certain.