All transaction in my current entitlement returns as .unverified

Im building a small iphone app with StoreKit and currently testing it in testflight right on my mac, not on iphone. StoreKit part almost exactly copied from SKDemo from one of the Apple's WWDC. For some users and for myself Transaction.currentEntitlements always returns .unverified results. I double-checked Apple Connect settings, i checked my internet connection and everything is fine. Is there some pitfalls for testflight on mac? How can I find out what is causing this problem?