Remove Sleep
Press the Menu button and press OK for Display, then choose Sleep as Never
Setting Date and Time
First try pushing the purple TEAMS button and if that doesn’t reset it, go into Settings and update the date/time.
Resetting the Phone
If a physical phone starts flashing, it might take 2 restarts to reset it. It will generate a code which needs to be entered here to activate the phone: https://login.microsoftonline.com/common/oauth2/deviceauth