Rated 2 out of 5 stars

This add-on worked fine up until firefox 47. Now it will only detect one monitor. No graphical image for second monitor in menu's - no longer moves window to second monitor when you press the tool-bar button.

UPDATE: My OS is Windows 7 64bit and I am running version 7.2 of your extension. No relative information in the browsers console.

If I manually move the browser to the second monitor, the graphical interface on the tab no longer works. As soon as I move the browser back to my 'main' screen the interface works but I can still only see that monitor.

I changed my main monitor and the problem is reversed.

This review is for a previous version of the add-on (7.2). 

It would be nice if you would at least report your OS, since I can't reproduce this on Windows 7 or 10 (or I would have repaired it). You should make sure that you run the latest version of this extension and you might want to check the browser console (Ctrl-Shift-J) to see whether anything related to Window Master is being logged.