Play videos with Lightroom 6.14 on Mojave

Hello community,

I am trying to play a MPEG-4 video with lightroom 6.14 on Mojave. The file extension is .mp4 (see attached screenshot).

I imported the video in Lightroom. I can hear the audio, I can see the progress bar at the bottom (with the frame preview), but I cannot the see video on the screen.

Is there a way to see this video? Eventually I'd like to capture a frame from it.

Thanks in advance for your help!

Paolo