Webhook response not working for new lead-instant (beta)

Hi, does anyone know why Webhook response is not working for new lead-instant (beta) and it does working with new lead-instant ?
If I select the new lead-instant (beta) option it returns me the following error:
"invalid appsecret_proof provided in the api argument".

Can I select the new lead-instant option and contact go immediately to my app?

Thank you
 
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