We have a TRIDVR-EL16M4 on system version 3.218.0000002.5 build date 2019-03-01 which the system says is the latest. One of the users noticed he can see the camera's on wifi, but will never load on cellular data. They are using Elite Viewer Pro version 2.1 on a iPhone 12. We have two older systems on the same app that he can view fine on or off wifi. I know the system itself is configured as I'm using EVP version 1.4 on my android (Samsung s23) and can view the camera on or off wifi. 

Any other app I can try on an Iphone? Tested on another Iphone 14 pro on ios 16.5.1 and it does the same.

To clarify Port forwarding is setup and they are accessing the cameras off site. With wifi turned on it works, but on 5G ATT it buffers then times out even with 4 bars for this one system only.