Hello,
I am new to this community but I can perfectly relate to your situation.
I had my male Syrian for about 2 and a half days and he is pretty much reacting the same as your hamster. He is hiding and sleeping a lot and when I am sleeping he seems to be a bit more active. Sometimes I place my hand holding a treat in his cage and sometimes he takes it and sometimes he ignores it and turn around.
I am guessing that we should let them settle a bit more and get them used to the sounds in the house. I also search for some advice regarding taming the hamster but I hope I was a bit helpful with this topic.
