Is this a new AP which you are trying to connect to the ZD? Or it is connected and unable to upgrade? What is the software version on the ZD and the AP? Is the AP and ZD on same location or remote location?
Good morning, the APs were connected during the update of the ZD1200, the current version of the ZD is 10.4.0.0 and before it was in version 9. After the update of the ZD the APs are only updating firmware all the time and the status is in red.
ZD should be in minimum 10.2 version if you want to upgrade to 10.4 release. If the ZD is in 9.x or below 10.2 version, I believe the APs will not be able to upgrade to 10.4.