I finally figured out a weird mobile data issue on my Unihertz Titan 2 with AT&T, so I wanted to post the fix in case anyone else runs into it.
My symptoms were strange. The phone had LTE service, calls and texts worked, and some apps like Facebook and TikTok would refresh. But Chrome would not load webpages, Reddit would not load, and other apps seemed to have no mobile data. Everything worked normally on Wi-Fi.
I confirmed the problem was not the SIM because the same physical AT&T SIM worked perfectly in both a BlackBerry KEYone and an iPhone SE 2020. AT&T had also provisioned the SIM using the Titan 2 IMEI.
I went pretty deep troubleshooting it. The phone showed LTE, data registration HOME, voice registration HOME, and the Android *#*#4636#*#* diagnostic menu showed the data service as connected. IPv4 ping, IPv6 ping, and the HTTP client test all passed. I also tried different preferred network modes, disabling 2G, disabling Adaptive Connectivity, changing Private DNS, moving the SIM between slots, and checking the AT&T APN.
None of that was the actual problem.
The fix was Network Manager.
When I opened the Titan 2's Network Manager, I noticed every app had:
Mobile: red X
WLAN: green check
So Android itself had a working cellular connection, but Unihertz's Network Manager was blocking almost every app from using it.
I enabled Mobile access for Chrome and it immediately started working. Then I tapped the main Mobile control at the top so the whole column became green. After that, Chrome, Reddit, and everything else worked normally over AT&T LTE.
So if your Titan 2 has signal and calls/texts work, but certain apps only work on Wi-Fi:
Check Network Manager before messing with APNs, ADB, or radio settings.
That one setting caused hours of troubleshooting for what turned out to be a simple per-app mobile data block. 😅
Source: r/UnihertzTitan · by /u/Large_Newspaper5743