Many users have reported that TeamTalk for iOS cannot connect to a server when it’s using mobile data on the T-Mobile network. When on WIFI it, however, works fine. The cause of this issue is unknown. To stay updated on the issue please follow the progress here.
Users are getting the operator updates?
This is required and provided by T-Mobile.
I’ve installed every Carrier update T-Mobile sends out to my phone.
I’m happy I don’t have this problem, because I live in New Zealand.