Red light on Hub 3

This came on a couple of days ago. I've tried switching off and on again and resetting. I even left it off overnight but the red light is still on. The box doesn't feel particularly warm but I have been unable to run diagnostics. Yesterday it didn't recognise the password, today I can get in and start running diagnostics but after it reaches 30% it throws me out and wants the password again then when I can start running the diagnostics again.

I would be pleased to hear and try any other suggestions - everything seems to be working OK and I could live with a red light instead of a green one unless it means that it is actually over-heating and could burst into flames!