I generally run Microsoft Teams Desktop app in Public Preview to see and test new features. However, in Public Preview I don't have access to the Power BI app in Teams.
So when I switch back to 'GA' mode I can see the Power BI app in Teams, BUT many of the conversations that existed in Public Preview are now invisible in GA mode! Effectively this means I'm stuck in Public Preview mode.
I've tried exiting and re-joining the team (in both modes). Microsoft Teams in the browser also gives the same strange behaviour. The team and most of the conversations were created while I was in Public Preview mode, the team has many guests and other users who aren't effected.