Long story short. If you have Firefox 64 installed and Rapise stopped connecting then run Registry editor (regedit.exe) find and delete the key:

 

HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Mozilla\NativeMessagingHosts\com.inflectra.rapise.firefox

 

What you need is to simply delete this node.

 

The reason for the issue is a change introduced in Firefox 64 affecting how the registry is read to load an extension. 

See:

https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Native_manifests:

As of Firefox 64, the 32-bit registry view (Wow6432Node) will be checked first for these keys, followed by the "native" registry view. 

 

An appropriate change to the installer will be introduced in the next fix-release of Rapise.