This Works For Firefox 56 users
(Thanks to user ae8425, for keeping my solution alive)
__________________________________

Download No Squint Plus version 50.0 from here

https://addons.mozilla.org/en-US/firefox/addon/nosquint-plus/versions/

You have to choose 'Download anyway'

This will download an xpi file (nosquint_plus-50.0-fx.xpi).

Save it anywhere you want on your PC (easiest is just the desktop)

Now drag and drop this xpi file onto your Firefox shortcut on your PC desktop (even if you have Firefox running).

You will now be prompted to install the Add On

And there you go. A working No Squint Plus for Firefox 56

PS; Set updates to 'Off'
_________________________________________________________


For some reason i cant find my original review, as i posted this before, so i post this again.
So here you go, this works flawless if your willing to stay on FF 56