Okay! I have cause of the problem now.
I fully decompile this app, RE the thing, trace it out.
I manage to strip out about 16Mb of Kotlin code, update API, fix old APKTools compiler code, and recompile. Not as much smaller as I would like, but now I can get much more data.
By running through my own loopback proxy, data comes in... connections, ports, etc.
When app gets to global data management block and begins loading GoogleAPis is where all goes poopoo.
tcp://[2607:f8b0:4009:814::200a]:443 is one of hundreds of addresses that app tries to contact.
These are all in a block range and belong to Google Ad Service DNS.
My first thought, my security killed the app connection, so I bypass.
No, still no data returned.
I open terminal app and ping android.googleapis.com
Complete packet loss.
I use browser and external ping and get 100% packet data good.
I contact tech support, and as I suspected, the carrier has firewalled this DNS due to all the ads and loss of bandwith they cause.
So, my modified app nor bypassing firewall, will ever make this app work for me without WiFi (as on WiFi I am not using secure data carrier).
And I even made this new icon for lite version.
At least now I know, the app is working, it is being stopped by carrier.