I'm trying to send an API call to generate the payload for an App Clips Rich Link in Apple Messages. My request has header and body like in the description in the image, and in the authorization header I have a valid secret and fresh iat stamp. but the request returns 403 forbidden status. Did it happend to anyone? Can some one point me to the problem?
https://register.apple.com/resources/messages/msp-rest-api/construct-payload