I would normally say it is possible for them to go off their food when in a new environment but usually they are eating when the owner isn't looking. Also bearing in mind your thread about red pee it makes me think that he may be in pain due to the possible UTI. I remember from your other thread that he had sore feet too (possible bumblefoot) so he really does need to see the vet as soon as possible to get him on pain relief and to sort out antibiotics for the possible UTI. Like I said on the other thread he may need an xray to rule out a stone too.
In the meantime, he needs syringe feeding if you are certain that he is not eating? have you ever done this before or would you like some guidance? If he is not eating at all you would need to try to get as much feed into him as you can so that his gut doesn't slow down. Is he pooing at all? Fluids are also important if he isn't drinking.
Have you weighed him at all?