P: Videos don't play and don't import

Hi Rikk, Again thanks for answering. There are no firewalls, virus detectors, corporate nanayware, or so. Not on my company mac or at home.
I have deleted all preference files, of all programs. Since is a pain in the *** ro reinstall everything (I have a lot of plugins for priemere and after effects with need to be deactivated first).
So, again Removed  adobe lightroom software. Reboot the mac. So no files of adobe lightroom remaining. Reinstalled lightroom, launched it. Same error. No import of video or playback of video.
I am running on Mojave (not Catalina). Since this errors occurs for me in version 9, no new software is being installed on my system since it occurred, apart from updates. Is their a list of programs using Dynamic Link? 

At this point, I would recommend looking at any common software you might be running that is interfering with the Dynamic Link Media Server operations.  Virus detectors, firewalls, corporate nannyware, etc are all places to look. Since you see it on two different machines I would concentrate on commonalities between the systems.  I've since tested your file on Catalina and Windows 10 as well and do not have any issues on my end. 

Hi Rikk, Hmm. nice for you.  But at my place in doesn't. I am kind of stuck on it. I have tried on a iMac Pro this last action. New user, new library. Nothing works. Specs 16 GB Radeon Pro video. Internal memory, 64 GB.
Error message from lightroom: An unknown error has occurred while reading the video file. Connecting to Dynamic Link server failed. (2)
It is a bit frustration, since I use lightroom a lot for catalogue of photo and video material.

I downloaded the video. 
Lightroom 9.2 - Mac OS 10.14.6
Video Imports
Video Plays
Video Exports

Hi Rikk. Here a  wetransfer link. Containing a video witch is not recognised anymore by lichtroom. https://we.tl/t-YS7Zq3NiLU

Have you shared a video with me yet for testing? I don't see one in my records. 

Hi Rikk, I have don what you suggested. Created new user and created a new Lightroom project. Same results. Video's will not be imported.

After two frustrating years I finally solved the video problem.
Bought a new computer.
I would like to thank Adobe for all their support over the past few years in trying to resolve the issue.
But I can't.

Hi Rikk, I will give it a try, although I have my doubts, but I'll let you know. I work with 2 different ligtrooms catalogs on different macs (but same version of lightroom). One is at home and one on my work. Both have the same issues with video.

If you create a new OS-level user account for test purposes, does the video work when logging into the new account?