Mike2hot2hold , via OnePlus 7 Pro , Sep 16, 2020 : I have AT&T and after the 10.3.4 update I've lost all my mobile data connectivity. This continued with Beta 18. The error I get says Android System login AT&T network. I've made sure data roaming is on. Reset and confirmed AT&Ts APN. Reset my network settings. Called AT&T and dealt with there customer service and tech specialist. They assured me that my phone is connected to their network. After all this I can only assume this is a system update issue. Please help, will be going back to office soon and need mobile data asap!