Can't install in 59.0.2 (64-bit) on Windows 10

So I just switched back from Chrome to FF. I tried to install Kee from and I got “This add-on requires a newer version of Firefox (at least version 56.0). You are using Firefox 52.0.” But I’m actually running 59.0.2 (64-bit) . On my Linux machine it just installed normally as one would expect.
I tried installing from the .xpi directly but FF won’t let me, even with the “xpinstall.signatures.required” switched to off.
Any ideas? Thanks.

Did you download Kee from ?

I am trying to…

How strange.

Do you know if you have any other add-ons installed or perhaps a customised user agent string?

This doesn’t really appear to be a problem related to Kee since it is the (AMO) website which is incorrectly detecting the version of your browser.

If changing or removing other addons doesn’t help, I suggest raising an issue on Mozilla’s GitHub account so they can help diagnose and fix the problem: