My hamster acts frantically on his play pen

[Luminity]

Hello i just got Rin (a hybrid campbell dwarf hamster) two weeks ago, Im a new hamster owner but I did research before I got Rin.
Earlier I decided to make a playpen for Rin (i just used books as barricade) and placed his toys, hideout and his food dish and water bottle. But when I placed him inside, he runs around and digs on the corners, I thought it was normal at first but several minutes passed his actions didnt change, it got weird. He digs frantically on his sand bath and food dish, I never saw him do that on his cage. And when I call him, he doesnt respond unlike when he is in his cage, he could easily tell if im near even if I dont call him.

Does it mean that Rin does not like play pen? Or should I continue to tame him using play pen everyday so he could get used to it?

(Rin is not fully tamed, he still gets nervous when I move my finger when he is near or when I stroke him. But he does get near my palm and take treats from me )