I'm having trouble registering webhooks on document libraries using the /subscriptions endpoint.
When I use ngrok as the noticafication URL on my local environment, I am able to create the webhooks and listen to events successfully. However, after deploying to the dev environment and using an AWS API gateway (public)endpoint as a notification URL, I get the following error message:
Failed to validate the notification URL 'https:/***********/webhook/sharepoint'
Interestingly, when I hit the same API from Postman, it works fine. The endpoint is active and returns the validation token in less than 5 seconds.
I also tested the endpoints using the SSL server test tool and confirmed the endpoint is set to TLS 1.2.
What else could be the potential issue here?