Plini unflavored yogurt is fine.
As ther have said, be patient
Cats need time to adjust to their new home and owner. It may take a few days or a few weeks or longer. You just go at the cat's pace. Dangle fishing pole toys at the cat to entice him to play and think " this person may be strange but fun to play with". If the cat doesn't want to play, don't push it. Do quiet activities in the same room as the cat so he gets used to your presence. Maybe something you are doing will pique his interest and he'll come over to check it out.
As ther have said, be patient
My Aby wasn't but I also got him from a breeder, not a shelter, and he was 3 months old. He literally ran out of his carrier and started exploring and running around. My rescue was 6 months when I got her and she was more typical (stayed in bathroom, didn't want to eat, etc) but warmed up in a few days.
It's also rare that a cat isn't afraid when they first arrive in a home.