Custom OpenID Connect identity provider -- "attributes required: [email]"

Hi, I'm attempting to write a custom OpenID Connect identity provider, and I think I've got everything in place. The login flow works up until Cognito calls my userinfo route, where it invokes my callback (configured in App Integration > App client settings) with an error "attributes required: email" (email is in square brackets, the amazon forum software changes that).

I've confirmed that my userinfo API is returning an "email" field in the response JSON, and the identity provider has scopes "email openid", and the app client has allowed oauth scopes "email" and "openid" selected.

I'm kind of stuck as to what to attempt next. Everything else appears to be working, but this last step is failing.

Edited by: caseypoint on Aug 30, 2021 3:37 PM