Hi,
thank you for you answer.
I just finished now and I explain to the community what happened:
The webhook listener was a webservice (ASMX): I realized that an ASMX webservice cannot accept
json arrays because the .NET dictionary raises a fatal error.
A not-array payload is working fine!!..but HubSpot send arrays…
I replaced the ASMX with a Powershell script and now everything is working fine: just completing the test
Thank You