Hello, I'm having the exact same situation as https://discourse.mozilla-community.org/t/unable-to-deploy-signed-add-ons-to-firefox-52-0-2-on-macos/14820, but on Windows systems. I have unpacked the .xpi file and distributed it using our Enterprise tool with activation of the extension through registry values. The extension seems to register well, but won't be activated / enable due to signature verification issues. When I install this extension manually using the same .xpi file (drag and drop), the extension gets activated, but of course is only installed and activated for that particular user. We are using the "release" update channel of Mozilla Firefox. Please help!