Just wondering what this actually means?

The LED on my brivis heater flashes 7 times then pauses. According to the panel this means "Valve Fault Lockout".
If I shut the system down (e.g. pull the plug) it will reset this lockout, about 24-48 hours later, it locks me out of the system again and refuses to do any work at all.

I have changed my Thermostat thinking it was this issue since it was playing up awhile back.

Looks like it is still locking me out. Any ideas?

Thanks in advance.