Dahua vto not connecting on dmss

[Loulou]

Hi, I recently installed a 2-wire dahua intercom system, with 2 vto and 2 vth, the entry door vto is connected to DMSS and works within the local network and on mobile data, but the vto on the gate, only works on the home wifi, and doesn’t work when the phone is on 5g,

I tried to play around with the network settings, but it still doesn’t make sense why would one work and not the other, any inputs are much appreciated

 

[dmcIPCAM]

You have probably already tried this, but confirming that you have one VTO set as the Main and the other one set as the Sub, and that
the SIP server settings on the VTH's are pointing to the IP address of the Main VTO?