ExtremeWireless Synchronization failed: SSID conflict for AP:<AP name> [<serial number>]
Changes made to WLAN services fail to synchronize with secondary wireless controllers configured to work in "High Availability (HA)" mode.
Synchronization failed: SSID conflict for AP:WS-AP2610 
Failed to save WLAN Service: SSID conflict for AP:WS-AP2610 
ExtremeWireless (formerly known as IdentiFi Wireless)
All firmware versions
High Availability (HA)
A rare situation where two more WLAN Services configured with the exact same SSID Name have been applied to a common AP. Therefore forbidding the target WLAN services to successfully synchronize between wireless controllers in HA mode.
Locate the AP.
Identify the conflicting SSIDs (WLAN Services).
Disassociate the affected AP from the conflicting SSID (WLAN Services)
At this point the affected WLANs should successfully synchronize.