HOTSPOT User Manager - ALREADY AUTHORIZING, RETRY LETTER

DEAR ALL,
We installed HOTSPOT SETUP (Authorization from Radius Manager ) for around 1000 students, with 6 UBNT Access point with 6 different SSID’s.

The problem is, when Students are roaming from 1 SSID to Another SSID he/she is getting login page option for another SSID and after he/she fill the ID PASSWORD they getting “ALREADY AUTHORIZING, RETRY LETTER” or sometimes getting error of “invalid calling-station-ID”


Please HELP ME ASAP