My strava account always automatically disconnects. The first time I connected it to Zwift, I used my facebook account to log onto Strava when prompted. I recently changed my FB password (not sure whether it is related).
No matter whether I re-connect with strava using my normal strava logon or the FB"key", while the reconnecting always succeeds, it always seems to disconnect almost immediately. Other connections (Garmin connect) seem to work just fine.