The SIM IP 10.229.231.95 is using the CGNAT, not real public IP, the port forwarding and only available to access on the Internet when the router WAN is public IP.
I am not familiar with cradle point, but if you build a VPN, and the server is public available, you could do a port forward to the VPN server which routes in the VPN to the GL-X3000.
Not what I would prefer, but depending on the needs maybe a solution.