How do you factory reset a castle- caretech euro-mini alarm panel?

Moved into new house where this alarm is fitted but after some building work front door magnetic sensor was detached from door frame and left and alarm indicated some fault. I re-connected it but I get an error that I need to contact the installer.

I don't know who installed it and I have no other pass codes apart the single user code we were given.

I can re-programme the panel if I knew how to reset it first.

Can someone help me to reset the panel, thanks.