Photoshop install - "sorry, your access has been denied"

Hi There,.

I work for a school and they've purchased 12 PS licences. I've created 12 email addresses, and for the first 2, everythig went as expected. When i go to No.3 i get the "sorry, your access has been denied". I've had a look here and on the wider web, but couldn't find anything.

Any ideas. 

Thanks in advance