[Error: There is already another active subscriber using the same receipt.]

Hi there,

→ I am purchase subscription with app userId 1 and using sandbox id 1
→ Now I am log out from the app and login with app userId 2 and using sandbox id 2 with same device

In time of second user purchase I am getting [Error: There is already another active subscriber using the same receipt.]. 

I understood that If I try with same sandbox id then it happens but with different sandbox ids don’t why it’s happen.