Our apps continue to function correctly on iOS 26 using StoreKit 1, with no observed compatibility issues.

The problem has been solved, because the region set by the sandbox account is different from the region set by the product.

What is causing the problem and how can it be fixed? ask for reply

I sovled the error. In my case, I changed the password of my appid , then i encounted the error。 So i checked my account in Xcode，and found the tip “Your session has expired. Please log in”。 I logged back in my appid in Xcode and sovled the error。