Data syncing error from Strava and Garmin - Does not pick power

I am new to XERT. I find XERT imports all data accurately on the indoor trainer (both when using XERT android app as well as when syncing historical data through Strava). However, I am seeing an issue with my outdoor rides. I record my outdoor rides using Garmin Vivoactive HR GPS smartwatch which is then synced to my Strava.
I have tried syncing data here from Strava, from Garmin connect as well as by directly uploading the FIT file. However despite all three methods, I am unable to see any power data and hence the XSS data for these rides.

Your watch doesn’t capture power - i.e. you cannot pair it to a power meter - on your (outdoor) rides. Power data is what drives Xert, but there is a HR derived method to calculate XSS.

I think that the RPM requirement (so HR combined with cadence) is no longer needed, just HR would do.

But you need to enable this option under ‘Account Settings/Profile’. If you know your resting and max heart rates, override the 'Auto-estimate- toggle…

(Strava does a power estimate, but that doesn’t go to Xert, as it is inaccurate on a detail level, albeit not that bad ‘overall’ as an indication of the average for the whole activity.)