Hi, from what I can tell you're using Mac OS 10.15 which is a beta version. We are still working on support for their beta version, I believe it may be released in the next Firefox version - 68.0.1 - but until that's released we can't say for sure. A workaround in the meantime could be to use a [https://www.mozilla.org/firefox/channel/desktop/#beta Beta version] of Firefox (69b3 or later) which [https://bugzilla.mozilla.org/show_bug.cgi?id=1563631#c8 I believe already has support] for Mac OS 10.15. Note that using the beta version should create a new separate profile, but changes in one version will not be reflected in the other.