Adding Hybrid Connect form into Category Description is possible.

For this you need to install a free plugin named "Widget Shortcode" 

This plugin Outputs a widget using a simple shortcode.

Example shortcode generated by Widget Shortcode plugin :-

[widget id="hybridconnect_widget-12"]

Go to your widget area & copy the shortcode generated by Widget Shortcode.

Now you can put this Short code into category Description field.

If it doesnt work, Please feel free to contact technical support & mention this solution in your ticket.