I’m observing the same behaviour in our app. An instance of our app, that’s loaded in an iFrame in a different 3p-app fails with the same error:
CallbackHandlerError: Callback handler failed. CAUSE: Missing state cookie from login request (check login URL, callback URL and cookie config).
Inspecting my browser tools, I see the Set-Cookie differs in the development environment, and when run in an iFrame context.
The difference is that
this error comes up implying SameSite needs to be configured in particular way. Though, my origins go across http and https, which seems to be in contention with setting SameSite = none
Haven’t noticed this behaviour before…