Can't Install Dark Mode Add-on after downloading, it always appears this message from ff since 3 days: 'Can't install Add-on because it seems to be broken.'
The problem happens to all older versions, too!
My ff version etc. is supported.
I even have the support for chrome addons installed (chrome store foxified) to fit better with webextensions -the problem persists.
Just wanted to inform you about the issue.
Please fix it & make it installable again. ff 48.0.2 on Mac Tyvm :)