Check with whoever takes care of that wifi access point. The "AP currently in use" message could mean no more DHCP slots available, or the access point is being so heavily loaded that the available bandwidth is unacceptably reduced, or some other setting or problem that's preventing you from using it. I'd have to see screen shots of the access point to do more than make guesses. (Probably even that wouldn't be enough, and I'd have to be there. The person who administers the access point is already there.)