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.
After upgrading to v4 I have lost my TitleBar buttons and I cannot add them back. After clicking Add and completing the window nothing is added to the list.
Excellent, glad to hear you were able to get it sorted out, and thanks for posting the solution!
I'm not sure why the PNGs would have ended up being invalid after updating, but I'll keep this info handy in case anyone else runs into the same issue.