I'm using Firefox Developer Edition v79, and I've been getting plagued by a particular issue for a while, but only recently found a bug report that clued me into the cause - and it's specific to the portable version only.
Firefox prohibits extensions from working on their own site (specifically, addons.mozilla.org). In order to allow extensions to work on this protected site, you have to do the following in about:config:
- Clear the contents of "extensions.webextensions.restrictedDomains".
- Create/Set "privacy.resistFingerprinting.block_mozAddonManager" to True.
However, it turns out that there is a problem - when "privacy.resistFingerprinting.block_mozAddonManager" is set to True, you can't install addons from addons.mozilla.com. They fail with the error "The add-on could not be downloaded because of a connection failure."
You can still manually save the XPI file and install it by pointing the URL bar to the local path - but direct installs from Mozilla's site will not work.
But here's the real issue - this problem ONLY exists in the portable version. In the normal installed version, setting "privacy.resistFingerprinting.block_mozAddonManager" to True doesn't cause the problem with installing extensions.
Is this something that is fixable?