During all rides I tried this morning (Saturday 11th april 2026 - from 7am to 11am UK time) the Apple Watch after pairing and transmitting HR after a few minutes (maybe 10) loses paring and can’t make it to work again even if the paring screen shows it connected.
After closing Zwift on iPhone can pair it again but loses paring again after a few minutes.
Rebooted both iPhone and Watch (and even re-installed Zwift on Watch again). But it kept the same behavior.
Thursday (April 9th) all worked OK (did a 1h race and no problems) and no changes in any software version since on any device.
Zwift dropped support for their Apple Watch integration years ago, so unless they revisit that, the recommended solution is do not use the Apple Watch. Buy a heart rate monitor instead.
Some people have success using the Heartcast app on the watch so you could try that and see how it goes.
Using the Apple Watch is a bit hit‑and‑miss. Interestingly, it works much better with the latest version — it now connects instantly in most cases. If it doesn’t display in game or selected on your Apple Watch, then close the app on the watch and reopen it. You might need to repeat this several times (sometimes 10-12 times) until it finally establishes the connection.
If the Apple Watch disappears from the list of available HRM connections, close and restart all the apps.
By the way, I usually start the Zwift app on my iPad first, then open the Companion app on my iPhone. After that, I tap my profile on the iPad. Once it gets past the connection screen, I go back and wait a few minutes to make sure it keeps the HRM connection.