Maximum SSID in OAW-AP-1321
Could it be that you are trying in Express mode? Have you tried OV2500/OVCirrus mode? I would never recommend configuring more than 3 SSID's per radio. Since wifi is a shared medium where only one device can access the medium at any time, around 75% of the frames transmitted are control and management frames (e.g. overhead). Each SSID increases the overhead created (see WiFi SSID Overhead Calculator – Wireless LAN Professionals (wlanprofessionals.com)).
In ap1320 datasheet:
•Capacity • Up to 16 SSID per radio (total 32 SSID) then 32 SSIDs for the AP. Datasheet is correct due this point. Thanks