AP 55C powers on but no Ethernet communication

I have an AP 55C that was working fine one day and not working the next. 

When I plug the AP, I get at first a solid green light for 27s, then no light for 7s, after that a slow flashing green light for 12s and then a slow flashing orange light for 1min and 49s.  Then it starts all over again.  According to https://community.sophos.com/kb/en-us/122791 , the AP has booted and now there’s no connection to the firewall. 

The two lights beside the RJ45 plug do not light or flash and the light on the switch also do not light or flash when plugged in.  I've tried a different switch, Cat 5, PoE injector and nothing works.  The AP 55C was plugged to an XG Firewall and now to a UTM 9 and nothing shows up in the logs.  When I plug another Sophos AP (AP 55) in the same setup, everything works ok.

I'm a home user and no Sophos expert but would greatly appreciate your help.