Adobe Bridge 2020 not showing mp4 video thumbnail

Bridge 2020 stop showing thumbnail of video (.m4v  and .MOV) thumbnail.  

I turn on use software rendering, as well as highlight each video to purge Cache for that video.

The first 1 or 2 video I purge Cache show the thumbnail.  But when I did the 3rd one, nothing happen.  

Besides that, Bridge freeze, I could not purge cache anymore.  

I have to restart my computer, if I'm lucky, I can purge 2 more, but then Bridge freeze again.

I have hundreds of video, please advice.

Half year ago, before I update Bridge to the new version, I can see both video right away.  I could not work at all now!!!

I just update my bridge to the newest version, and no luck.

Thanks