@Ayoub:
I see Cloud4Wi's web site has instructions on how to configure different AP types, including some Aruba APs, but they don't seem to publish instructions for Aruba Instant On. As such, it is hard to say what this "Identifier" field relates to in the Aruba Instant On configuration.
When you talked to them, did they understand there is a difference between the two product lines?
Anyone else has experience with setting up a captive portal with Cloud4Wi?