Not sure why the router log didn't show anything for the OpenVPN connection.
This is the openvpn log from the phone:
[May 15, 2023, 09:01:59] Transport Error: Transport error on 'XXX
.asuscomm.com: NETWORK_EOF_ERROR
[May 15, 2023, 09:01:59] Client terminated, restarting in 5000 ms...
[May 15, 2023, 09:01:59] EVENT: TRANSPORT_ERROR info='Transport error on 'XXXX
.asuscomm.com: NETWORK_EOF_ERROR'
[May 15, 2023, 09:02:04] EVENT: RECONNECTING
[May 15, 2023, 09:02:04] EVENT: RESOLVE
[May 15, 2023, 09:02:04] Contacting XXXXXX via TCPv4
[May 15, 2023, 09:02:04] EVENT: WAIT
[May 15, 2023, 09:02:04] Connecting to [XXXX
.asuscomm.com]:XXXX (XX.XX.XXX.XX) via TCPv4
[May 15, 2023, 09:02:04] TCP recv EOF