I assume you're using a hotspot(?)
That's what I'm using and currently, I'm able to get into the game. You said you only turned your phone off and not the internet itself? Why not just switch the internet on and off & by this I mean your hotspot.
You could try seeing if your data has been used up, full(?) And maybe it's running much slower than before.
You could contact the company to check your data as well and see if anything changed or if your plans changed.