Why is Avast blocking your site when there has been no problem up until now.

It seems like a false positive result from Avast. It is quite common for Avast to block scripts that seems suspicious in their end. You might need to contact them directly by following their forum in this link: https://forum.avast.com/index.php?board=4.0. Or you can whitelist it on your Avast antivirus, I am not quite familiar with Avast so I am not sure about the menu of it.

My antivirus Eset does not block JotForm, it might be isolated on Avast perhaps? Do let us know if that helps.