Cannot add addresses in Configuration Rated 5 out of 5 stars

I am giving 5 to this provided my problem below can be solved.

I may be having the same problem as FourTwoOmega. When I key in a webpage to add to the list it disappears as soon as I press 'Add Site' and nothing gets added. I have tried with several different addresses. Could there be a conflict with another add-on or do I need to change any settings in Firefox?

This review is for a previous version of the add-on (2.0). 

Can't add addresses?

This could be a conflict with another add-on, but is likely a corrupt profile. Try creating a new, clean profile and installing only Force-TLS. If it works, then migrate your bookmarks and stuff over and start installing other add-ons.