Students unable to join world

I have 2 teachers who have some of there students unable to join their worlds.  They are on ipads using the Minecraft Education app.  We have tried having the students log into Minecraft on a classmate's ipad that is able to successfully join worlds.  This worked.  So it seems there is something about the ipad that is affecting the joining of worlds.  However, when I look at the comparison of the ipads in our MDM the successful and unsuccessful ipads have the same iOS, same ipad model, same version of Minecraft app.  So I am stumped.