Did they generate a new password or give you the same one? Have them generate a new one... tell them why you need to reacitvate and they'll know what to give you.
Could be an issue with .75 or something else. I guess you'll need to wait and see if someone else is having similar issues... this is why it's sometimes not a good idea to run a leaked/BETA OS if you depend upon full functionality on your device.
Call IT again. I had issues trying to reactivate initially after upgrading to .75 and I called IT again and then retried activating and it worked fine. It's not the OS, it has to be something on their end.