webhook_delivery_sources_invalid
HTTP 400invalid_request
delivery_ is not valid: it names no key and not the portal, too many keys, or a key that is not your organisation's, not in the endpoint's mode, or revoked.
Handling it
Fix the request and send it again. message says what is wrong, and param names the parameter where there is one. Keep the request_id: it lets Parasend find the request.