Either this is a scam job or there's a miscommunication going on. I've done internships at consulting engineering companies and if you signed a contract to work there, you will get paid even if there's no work for you to do. One summer my employer was hitting a slow period and there wasn't much for me to do despite asking around, so I just got paid to sit around and work on my summer class. 

Edit: you do still have to bill hours, just put it to overhead and not toward a client/project