video preview is black

Hey Guys, So this weird things its happen and I have no idea what is wrong, I've tried enoumerous things but with no sucess. So I can't see the video on the window, but I can hear it, is just black, I tried different formats but still the same, and at the end If I export the project it will export with the video. But obviously If I can't see it, I can't edit. Anyone with any idea here? I also changed the media view and all other option that I could find online.

Thank you

I'd reboot the Mac, if that doesn't help, try trashing your preferences

idustrialrevolution.com/blogs/tutorials/...t-pro-xs-preferences

Turn off background rendering then delete all render files then relaunch.

Same here. Sometimes it will go away by itself with a FCPX restart, sometimes I need to delete the library cache, sometimes I need to delete FCPX prefs. I have found no permanent soltion yet. It adds a certain sense of adventure to editing.