Digging through forums has shown this type of complication (with the video cache filling up and unable to be purged, the failure to connect to dynamic link server) has been an issue FOR YEARS now and still not fixed. I'm not asking for Lightroom to support full video editing, I just want to be able to import and catalog video files along with the photos, without worrying about whether some were missed or cannot be read, etc.
2. Opening "Activity Monitor" and look for those same processes as on Windows. i.e "dynamiclinkmanager" ( I picked "dynamiclinkserver" too)
3.With those selected click the top left octagonal icon - (it was nice clear red stop sign previously but is now just another oh so cool but unclear grey Mac graphic) that should kill those processes,
4. Reopen Lightroom Classic and try importing the MP4 videos, this worked for me.
1. Uninstalled and reinstalled the latest Lightroom Classic
2. Deleted the Dynamic Server folder
3. Opened Activity Monitor and quit the Dynamic Server processes
4. Disabled the Splash screen when starting Lightroom Classic
5. Changed all my .MP4 files from opening with Quicktime by default to now open with VLC
6. Tried to open the video files directly with Lightroom via 'Open With' in the Finder
7. Used Clean My Mac 3 to see if that helped. It didn't.
Nothing works. All my software is up to date. The files are from a Lumix G9 & GX8.
Adobe are you working on this problem?