As Destiny suggested, likely relocation stress. Some dragons experience it, some don't.
It is common for a dragon in a new place to hide and sleep for a while, refuse food, or act skittish or aggressive when being handled.
It can also upset their tummies and cause diarrhea as you mentioned in another post.
Older dragons also might not eat as frequently as younger ones, some prefer to only eat once a day, and there are quite often days where my guys totally ignore their salads for no good reason. Older dragons require more greens and less bugs, too, so he might not be as eager to hunt as he is for a yummy salad. Some dragons lose interest in certain foods as well, and it's not uncommon for them to just start refusing to eat crickets in favor of worms, etc.
Just keep offering fresh food, and he'll eat when he's hungry. If he stops eating completely for more than a few days, that is cause for concern.
It might be a good idea to give him some space and let him get used to his new surroundings.
Talking to him and petting him when you offer food is great, but try not to handle him too much until after he's started showing interest in exploring, as it might be overwhelming.
Seems like you're doing an amazing job trying to learn as much as you can!
Keep us updated!!