If you downloaded DisplayFusion 12.0 and are having issues with languages please re-download and re-install. We have repacked the release as 12.0c with the languages fixed.
I have three monitors and the only one that will display the Windows 10 start menu is the one that is set to default monitor. I have tried to change settings to get it to work again but I have not been successful.
Thanks! Looks like this is related to an open issue on our list, so I've added your info. We'll be sure to let you know as soon as we've gotten it fixed up.
We've just released a new DisplayFusion beta version (https://www.displayfusion.com/Download/Beta/) and this issue should be all fixed up. Please let us know if you run into any trouble after updating.