I had the same problem. I found that other people are also giving feedback, but the feedback is not many, I do not know why? If Apple doesn't fix this problem, it could be disastrous. I responded in this discussion:https://developer.apple.com/forums/thread/792437?answerId=848401022&page=1#848866022

I ran into the same issue and found that in iOS26 beta3, not only did the old StoreKit finishTransaction method not work, but also the StoreKit2 finish method did not work. When will Apple fix this? How do I report this to Apple? If this problem is not solved, it will have disastrous consequences.