Are you using this on mobile or desktop? Does the extension error out?

If you are using it on mobile you need to manually activate the tabs that you want to export the history for. (see https://bugzilla.mozilla.org/show_bug.cgi?id=1583281#c17)

Also these are the settings I used to test and export my own tabs' history from my android phone:
> "Debug" - to get some useful logging
> "Time to load page (ms): 5000" - you might need to increase this