Hey,

Thanks for your review.

There is an issue with Firefox that prevents Add-ons from being installed/running.
Mozilla is working to resolve this issue.

As per their blog:
"Late on Friday May 3rd, we became aware of an issue with Firefox that prevented existing and new add-ons from running or being installed. We are very sorry for the inconvenience caused to people who use Firefox"

You may read about it here -
https://blog.mozilla.org/addons/2019/05/04/update-regarding-add-ons-in-firefox/

It should be fixed soon.

Thanks!
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