lsmzml Welcome to the community!
"You need to open the ports on your modem for the internal IP address that the VPN uses:
Portability refers to the network environments from which the VPN client can connect. By default, IKEv2 uses IPSec, which requires UDP ports 500 and 4500, and ESP IP Protocol 50. You cannot disable IPSec. By default, L2TP uses IPSec, which requires UDP ports 500 and 4500, and ESP IP Protocol 50."
A tutorial how to configure the ports can be found here.
Greetings
Daniele