I have a customer with 4 AP's that has been working to years.
They called me a couple of weeks ago as one of them turned red.
I replaced it with a demounit at moved this unit to the tenant.
It boots and I can even log into it with SSH but it is not seen by the cloud. It keeps flashing red.
I then connected the replaced AP to a PoE switch and it shows the same behavior.
This doing this another of their AP's went offline in Cloud Manager. It's still visible on the local network.
The two remaining AP's on the same subnet, connected to the same switch. is still working :-)