Steve,
A very warm welcome to Beoworld...
Given that the error message is displayed on the screen means that the power supply and HT voltage lines are working correctly.
The most likely problem here is going to be a microprocessor fault or something external to the processor which has triggered the fault.
When this error comes up does any function of the remote or buttons work ? I think the answer is going to be no, and if so, then this is certainly a microprocessor fault.
I suggest as a first step, you disconnect the system completely from the mains including link products and leave for 15 minutes and then power it all up again.