Client error: POST https://graph.facebook.com/v17.0/xxxxx/messages
resulted in a 400 Bad Request
response:
{"error":{"message":"(#100) Invalid parameter","type":"OAuthException","code":100,"error_data":{"messaging_product":"wha (truncated...)
Please be more specific when posting here and asking others for help, so do at least include you full request (w/o any sensitive data).