Doesn't work with firefox 66 in Linux

[ndias]

In Fedora with Firefox 66.0.2-1.fc29 doesn't work anymore, if I downgrade to a previous version of Firefox works as expected.
Unfortunately I can't see any error in console or anywhere.

[minfrin]

We've just discovered it doesn't work with Firefox 66 in Windows 10.

The browser console shows the following:

stderr output from native app signtextjs_plus: Could not detect profile directory

[jasp00]

The add-on works with Firefox 66.0.5 on Debian Linux. Make sure you have enabled "Debug to console" in the add-on's preferences.