Are you using the correct username and password specifically for openvpn and not the prontonvpn account?
How to manually set up port forwarding
https://protonvpn.com/support/port-forwarding-manual-setup/#:~:text=To use port forwarding%2C add,suffixes supported by Proton VPN.
How to log in to Proton VPN
https://protonvpn.com/support/vpn-login/
https://github.com/binhex/documentation/blob/master/docker/faq/vpn.md
Q27 worked for me.
VPN_OUTPUT_PORTS: 2468
Using my unraid ip address and not the docker hostname.
curl -XPOST http://192.168.2.222:2468/api/webhook --data-urlencode "name=%N"
The cross-seed docker logs confirms search for cross-seeds after torrent download is completed.