Final Cut Pro X Timeline is gone and red

I'm running FCPX v 10.3.4 under Mac OSX Sierra 10.13.1

I just started this library/project a week ago and now the timeline is gone and turned into red.

I tried resetting the settings and it was useless the problem persisted. What I did at the end is rescue the backup file and from there started again to avoid delays on my deliveries.

This issue concerns me because it can happen again and my work could be lost.