403 Forbidden when try to access the custom domain

Question

`{
    "message": "Forbidden"
}`

When trying to access a custom domain, the API Gateway REST response code is 403.
The API Mapping has been set up.
The following notice appears while attempting a direct API call:

`{
    "Message": "User: anonymous is not authorized to perform: execute-api:Invoke on resource: arn:aws:execute-api:us-east-1:************:xxxxxxxxxx/dev/POST/v1/notification"
}`

Accepted Answer

Hi 
403 Forbidden “anonymous is not authorized to perform: execute-api:Invoke on resource:” errors usually occur when the caller isn't authorized to access an API that's using IAM authorization. Or, the API has an attached resource policy that doesn't explicitly allow the caller to invoke the API.

To learn more about troubleshooting API Gateway 403 error visit link [1]
That said, to further investigation this issue we’d require additional details. I recommend opening a support case with AWS Premium Support using the following link[2]

Reference:
[1] Troubleshooting 403 errors - https://aws.amazon.com/premiumsupport/knowledge-center/api-gateway-troubleshoot-403-forbidden/
[2] Create Support Case https://console.aws.amazon.com/support/home#/case/create.

403 Forbidden when try to access the custom domain

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