FCPX Weird Proxy Issue

If anyone can shed light on this i'll be massively grateful.

My imported 4k FS7 files have the 'Transcode to Proxy' box greyed out. They are not already transcoded, i've checked, as when I select to View in Proxy mode I get the red 'Missing File' overlay in the browser. I have tried re-importing, same thing happens. Infact even if I re-import and select 'Transcode to Proxy' on import, nothing... No idea what's going on, could my Library be corrupt? Am I missing something really simple?

Thanks for any info. I've tried deleting preferences, didn't help.

Solved!

For some reason, FCPX had created Proxies but they were all literally a video file that had the 'Missing File' sign as the video?!! Found them by going to the finder location for my Optimised media and trashing them and the proxy folder. So strange. Anyway, i'll leave here incase anyone else gets the issue or wants to add why this could have happened. Thanks