Firewall (?) problems using Mozilla VPN

Hello.
I've downloaded and installed Mozilla VPN and currently using on 30 day trial.

I'm running Ubuntu 20.04.2 LTS.

The VPN works fine on my Android Tab & phone. And of course on my Ubuntu PC.

Unfortunately I can't connect via ssh (on a high number port, not default port) from my Android boxes to my Ubuntu PC if the Mozilla VPN is running on the PC AND my firewall is ON.

My firewall is Gufw v. 20.04.1.

My firewall works fine when the VPN is OFF - I can connect via ssh to the Ubuntu PC.

And I can connect via ssh to the Ubuntu PC when the VPN is ON but the firewall is OFF!

I should add that Wireguard is installed though not active afaik, could this be an issue?

I'd be very grateful for advice - maybe suggestions as to which log files I should look at.

Or suggestions for change(s) in firewall settings needed to make firewall play nicely with Mozilla VPN.

Many thanks.

Output from sudo ufw status (xxxx is my high number port for ssh):

Code:Status: active

To Action From
-- ------ ----
993 ALLOW Anywhere
587 ALLOW Anywhere
443 ALLOW Anywhere
80/tcp ALLOW Anywhere
22/tcp ALLOW Anywhere
xxxx ALLOW Anywhere (log)
192.168.1.20 xxxx ALLOW Anywhere (log)
192.168.1.20 xxxx ALLOW 192.168.1.6 xxxx (log)
xxxx (v6) ALLOW Anywhere (v6) (log)
993 (v6) ALLOW Anywhere (v6)
587 (v6) ALLOW Anywhere (v6)
443 (v6) ALLOW Anywhere (v6)
80/tcp (v6) ALLOW Anywhere (v6)
22/tcp (v6) ALLOW Anywhere (v6)

xxxx ALLOW OUT Anywhere
993 ALLOW OUT Anywhere
587 ALLOW OUT Anywhere
443 ALLOW OUT Anywhere
80/tcp ALLOW OUT Anywhere
xxxx (v6) ALLOW OUT Anywhere (v6)
993 (v6) ALLOW OUT Anywhere (v6)
587 (v6) ALLOW OUT Anywhere (v6)
443 (v6) ALLOW OUT Anywhere (v6)
80/tcp (v6) ALLOW OUT Anywhere (v6)