offline could be in two cases:
- wrong network setup (wrong port forwarding rule, wrong external address, WAN IP not match the public IP, wrong or absent a firewall rule, aggressive antivirus)
- unsigned identity
So, please, check everything:
4G very rare have a public IP (the WAN IP usually not match the public IP). The port forwarding will not work with it and node will be offline. Perhaps you could enable a public IP address if your cellular operator offers this option.
The identity files could be in any folder. When you run a node you will specify a path to it in the --mount type=bind,source=place/your/path/to/identity/here,destination=/app/identity