I've updated to LumaFusion 2.0 and now have missing media (red-striped clips) in some projects

This issue is occurring for some users when updating. We apologize for the inconvenience.  

In most cases, double-tapping on each clip with red-strips will force it to re-download again.

If this does not resolve your problem, you can manually replace missing media clips by dragging the correct media from the library onto the clip.