Asus Merlin OVPN not working

[umanoid 0]

Ive had this working for years (literally) but somehow after shutting down my QNap server (setup to use the VPN through Asus Marlin) I find the VPN isnt working. I tried a new AirVPN config but everytime I try and upload the config file to the router it fails. As soon as I upload it the screen flashes and returns to "No file selected."
Anyone able to help please?

[umanoid 0]

Checked the logs and am getting;
 Linux ifconfig inet6 failed: external program exited with error status: 1
Jul 31 11:08:46 ovpn-client1[2059]: Exiting due to fatal error