If you are submitting data on the Form but it is not posting correctly or displayed as "Nil" in your WebHook, this is generally caused by duplicate field Titles on the Form.
WebHook parsing is a one-to-one from Form Fields so if you have multiple fields on the Form with the same title, this will affect how/if the data can be sent to your WebHook. For instance, if you have two+ fields on your Form titled "Name" or "Email" the WebHook will post the data from the second Field with this title. If the second Field was submitted with no data, the WebHook will post "Nil" since the later Fields will overwrite the first Fields.
To correct this, you can either change the Title of the duplicate titled-fields to be slightly different such as "Your Name" vs. "Name" -OR- change the WebHook to post Field IDs (see below). Once this is done, you can rerun previous submissions to your WebHook to test out the postings or submit a test Form to see how this data parses over.
Submissions can be rerun by going into the Form > Submissions tab > click the submission > click on a submission in your database and here you will see a puzzle piece icon with a red badge on the right side of the submission. Click on the puzzle piece and click "Run Again" next to your WebHook.