The model number is ***** and it is 5.5 years old.
Yes, I have and just tried again. No response.
What is the key button?
No, I cannot set the clock. I assumed that is because I think the key lock is on - it is brighter colour than the other symbols. I would add that I have two identical ovens and it affects both of them. I have switched the ovens off for the several minutes and then pressed the lock key symbol for 15 seconds as you suggest. Nothing changed and I cannot set the clock, which means the oven will not work.
I have tried this, again having switched the oven off at the mains for a few minutes first. Everything continues to flash.