Can't connect to Access Point (WAC120) though signal is excellent

Model: Netgear WAC120 access point

Firmware: 2.1.6

I get bad wifi in my upstairs bedroom so wired this access point and have had strong wifi for about a year. Last week we had a powercut and I noticed the next day that my android TV wouldn't connect to the AP, it showed a strong signal but no internet. I think my tablet still connected but it may have defaulted to the downstairs router and I just hadn't noticed.

Anyway I tried multiple reboots and restoring to factory settings. I have now updated to the latest firmware 2.1.6. Where I am now is the AP works, I can access its settings on my PC, green lights on the device for wifi and internet, and it shows up as a strong signal on all my devices, but I can't access it with the wireless key. I haven't changed this at all, it's still the one printed on the base of the unit and I've been very careful to enter it correctly. But my devices always time out trying to connect.

I also tried forgetting the network on my android tv and mobile phone.