Thanks for pointing this out — you're right that our product identifier (istanbul.membership.monthly) doesn't follow the bundle-ID-prefixed convention (e.g. com.mehmetozenen.ustaistanbulapp.membership.monthly). One thing that makes me hesitant to attribute the root cause to this alone: this exact identifier has worked correctly for months, with real successful purchases as recently as Aug 23, 2026, and broke abruptly on Aug 24 with no changes on our end. If the naming format itself were the fundamental problem, I'd expect it to have failed from day one rather than regressing suddenly. That said, is it possible something changed server-side in how StoreKit resolves/validates non-namespaced product identifiers around that date? If you know of any related StoreKit backend change or have seen this pattern before, I'd really appreciate more detail — this is genuinely useful to bring back to my DTS case.