On Linux, disabling Firefox updates in Firefox itself will not fix this issue, because Firefox’s own updater doesn’t actually have this bug! You get this warning when the Linux package manager has already replaced the files underneath the running program.
You say it’s windows, but I think you said it’s a work machine so maybe they’re updating firefox from under you?
Restart Firefox to let it finish updating. I don’t think I’ve ever seen a screen that says you HAVE to restart right now at this very moment.
I got it again unfortunately, here’s a screenshot of what it looks like
I found this. https://superuser.com/questions/1451210/how-can-i-make-firefox-stop-forcing-me-to-restart-my-browser
You say it’s windows, but I think you said it’s a work machine so maybe they’re updating firefox from under you?