Remote User Access - Win 10 connection issues

Hi there,

One of our clients has a customer that works from home that until recently was able to VPN to the office using their Remote User Access profile.
For some reason, this has recently stopped working and instead throws the error:
“A connection to the remote computer could not be established, so the port used for this connection was closed”
And all other profiles created in Remote User Access aren’t working either
I’ve tried:
Deleting and recreating the VPN profile
Creating a firewall rule allowing all traffic from that IP and/or L2TP ports (UDP 1701)
Rebooting router
Updating router to 8.0.0 firmware (I’ve heard there’s issues with 8.1.1, don’t know how to update it to older firmware)
Creating new RUA profile with varying password security
Changing PSK
Creating Windows firewall allowance for UDP 1701
Attempt VPN connection to a different Peplink router with RUA (which was successful)

Not sure what else try, help is very appreciated