I’ve just found the same issue as Ben. A blank green screen but audio still present and no indication of media offline or lost links. This is with the same files which performed solidly the last time I opened these projects….and had done so for 2 years prior to that….they were long-running edits and FCP never let us down.
So nothing to do with wrong formats/codecs or settings. And nothing wrong with the gear as recent imports are playing sound and picture as expected.
Nothing about the set-up or hardware has been changed since the projects ran correctly so could there be some date-specific bug or other update getting in the way? Can media just go off after a few years?