are you quarantining the tortoise?
I made the mistake of not doing with mine as i didn't know better, and both ended up having several trips to the vets.
Just trynna save u some money
it could simply be a case of settling into his new environment. Give him daily baths to keep him hydrated as he isn't drinking and eating to much. It also encourages tortoises to go to the toilet.
Make sure ur sprinkling their food with limestone flour, for extra calcium, and nutrobal 3-4 times a week. to stop any growth deformities.
give him about a week or so to settle in, with the new bathing regime, and just see how he gets on.
If he isn't eating it's no cause for immediate concern as tortoises can go weeks and months without eating quite happily. it's the drinkin thats more of a worry, just make sure u keep him hydrated,n if still worried then take him to the vets and just explain ur concerns.
hope this may help a little
Katie