ChatGPT App added via “+” is recognized by Instant/Thinking, but GPT-5.5 Pro often cannot 'see' the app or its tools

Thanks for digging into this, @NatKSS, and for sharing the article. You're correct. App integrations are not currently supported in GPT-5.5 Pro, which explains the behavior you were seeing. I agree that a clearer message from the model or UI would make this much easier to understand and troubleshoot. I'll pass that feedback along to the team. -Mark G.