We are also having this issue. My daughter is using Teams for school on a Google Nexus 7 tablet (running Android 5.0.2) and it worked fine on Thursday and Friday, but Monday it would not connect to any classes unless we hit "Join" over and over for 5-10
minutes. It would make the connecting screen and sound, and then go to a black screen that said "We cannot complete the call." On Tuesday it took 20 minutes of hitting "Join" repeatedly to connect to her first class. After that, we uninstalled and reinstalled
Teams, and it worked fine for the rest of the day. This morning, after hitting Join 5 times and getting the error message again, I uninstalled and reinstalled Teams and this time it did not fix the problem--although it did finally connect in about 5 minutes.
For comparison, my other daughter is also using Teams on her own laptop in the next room and has not had any problems connecting to her classes, so it is not our internet--it seems to be a device-specific issue. This is seriously interfering with my first grader's
schooling, though, so quick advice would be very much appreciated! There is nothing except basic programs on the tablet, and nothing running concurrently except Chrome and Teams.