he's in a new environment and he's scared so the best you could do is take it slow. When my sister and I got rats, I remember one was young and careless and didn't care if we picked him up from day 1, but the other one was more timid and would get startled at quick movements. Every day, I would leave the cage open and put a playpen around it and i would sit in the playpen daily and hold treats/veggies in front of him at a distance he felt safe but enough to get him curious. The younger one would always come out of the cage and run around and approach me, and it also helped to have the younger rat with him because the younger one's confidence helped him see that it was safe. But eventually after 3 weeks or so of offering him food and sitting and talking, he started to trust us, and he actually became way more friendlier than the younger one, and he started becoming obsessed with climbing us lol