Created webhook response is 403 forbidden

Created webhook response is 403 forbidden

I have created a webhook for Payment Success event in test organisation. First of all i was not able to provide my https url in the url part, it showing the message like 
  • We were unable to connect with the given URL. Please enter the correct URL and try again. 
Next is like created webhook is not trigerring the url its sending the response as 403 forbidden. I am using a POST request for the url and POST verbs are there at my server request. So could you please help on what might be the cause for this issue.

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