Please report the bug here: https://github.com/pistom/hohser/issues with details.
You can also try to install one of previous versions of the extension to see if it's an update that cause the problem.
https://addons.mozilla.org/en-US/firefox/addon/hohser/versions/
First you will have to remove the extension from Firefox but your domain list won't be removed.
Also this post may help: https://github.com/pistom/hohser/issues/84#issuecomment-510168920