This question already has an answer here:
This is only since the new update 0.37.0
I have been playing since the game came out in the UK and have got a Moto G phone
I log on using google accounts. I dont really want to start again as I have 104 different pokemon.
I can play fine on wifi, but can not connect on my mobile data. I have uninstalled the app and then reinstalled it, it didn't work, I logged in and out a few times to test it, and then I restarted my phone and the same thing again, the bar loads 1 bar and then comes up saying sign out.