This probably has nothing to do with your supervisor, but with the administrative staff in the department. August is like the "official academia holiday month", our department is almost empty, so it wouldn't be surprising if everyone is on holidays.
Also chase it up, you won't "offend" them. In my case, I accepted the offer, my sponsor send the contract to the school, and the school secretary somehow managed to lose it. So, I had to ask the company to sign a new contract (that stressed me out of my head), and after I managed to sort it out, the first "lost" contract re-appeared... Well...