Cannot import video .MOV files into Lightroom: Preview Unavailable

Dear all,

I hope you can help me:

I bought a new camera (Canon 5D IV) and I wanted to import my first videos into lightroom. However, I can't. It says "Preview Unavailable for this file".

In the past, I have been able to import videos and edit them. I've looked on several earlier topics, but none of them seem applicable or helpful. I've tried the DNG converter too, but this seems to only work for photos. 

Does someone know what I can do to make Lightroom recognize these files so I can edit them?

Edit: I tried converting the .MOV to .MP4, but Lr still doesn't recognise the file

Thanks so much!

Info:

Lightroom Classic CC

.MOV video files on the computer. They do play in Quicktime, Premiere Pro etc

Lightroom Classic version: 7.0.1
License: Creative Cloud
Operating system: Mac OS 10
Version: 10.15 [2]