Garmin has opened a thread in the Forerunner 255 Series for people that have problems with missing HRV Status and Training Status on their watch.
This is the thread:
Forerunner 255 Series: Missing HRV Status and Training Status on watch
Since several Forerunner 955 Series users also seem to be affected, it would be great if you could tell them here, so that they investigate this issue not only for the 255 Series but also for the 955 Series.
The problems concerns missing HRV status despite wearing the watch for 21 nights while sleeping. Others have reported that they're missing a Training Status and other parameters – like Training Readiness – despite meeting requirements to establish a Training Status on the watch. Some have reported both of these issues, but in different threads.
