Hmm, what happens if you right click and save-link-as on the .xpi link? Or if you download it via curl or wget or something?
Edit: That studies image looks like it has already been installed, which is weird if your extensions aren't back...
Edit: That studies image looks like it has already been installed, which is weird if your extensions aren't back...
As for the studies image, that's only half of the fix according to the blog post [1], mine is only verification-timestamp, not signing-intermediate-bug.
[1]: https://blog.mozilla.org/addons/2019/05/04/update-regarding-...
You're right about the image, that's weird, I can't think of any reason why the verification-timestamp one would be necessary.