Google Message RCS protocol error on OpenVPN

[Alaska99]

When I use my cellular without VPN connection I can send message with RCS protocol but I can't when my cell is connected to the openvpn server of my RT-AX88U. I can browse the web and acces my local network drive but Google Message is always in "try connecting" and after somes minutes ask me to sitch to SMS mode... I try with Instant Guard vpn too and same problem.
Someone else had this problem and how resolve it? Should I need setup port forwarding?

 

[eibgrad]

What happens if you use a *public* OpenVPN service, like PIA, NordVPN, etc.? I'm wondering if this problem is perhaps NOT specific to the router's VPN server(s), but VPNs in general.

 

[Alaska99]

You re right. I try with PIA and it block RCS too...
Thanks