I just installed Easy FancyBox – Pro on two different sites. When I went to test galleries on those sites, numerous issues occurred (lightboxes wouldn’t close, keyboard control would stop working on the third photo, the navigation and close controls vanished as I tried to use them).
I was about to come here for support, and I tried one thing first. I went to Settings > Media admin page, and I clicked the Save Changes button. After doing this, all issues have been fixed.