Lightroom CC: videos play on one iMac, not the other

[bradleykents]

In my experience, Lightroom CC has had some growing pains when dealing with videos, but it's improving.

But I've run into a snag ...

I shot four 5-second videos on my iPhone X, two each with the standard Camera app and the Moment app — one at a normal frame rate, the other in slo-mo.

On one iMac everything is just fine — I was delighted that Lightroom CC could deal with the slo-mo!

On the other iMac, the four videos appear (with thumbnails) in the Grid view, but in full-screen Detail view, only one (the slo-mo version from the Moment app) plays. The other three open in Detail view without a thumbnail and with the play bar slightly advanced but everything is frozen: can't move the playhead, no image, no play.

Both iMacs running High Sierra [10.13.3] and both running Adobe Lightroom CC [1.1].

I've restarted the iMac but that didn't address the problem. 

Any suggestions would be much appreciated.

Thanks,

Bradley

[99jon]

Do they play in the Safari or other browser window if you log-in to your Lr CC web App?

https://lightroom.adobe.com/

[bradleykents]

Good approach to troubleshooting, 99jon,

Yes, they all play in Lr CC on the web.

And, as I've described, on iMac- ... and yet not iMac-2.

And, oddly, on iMac-2, one of the videos plays, while the other three do not!

So there's some issue with iMac-2 that is otherwise running the same OS and Lr CC as iMac-1.

I'm wondering if there are perhaps preferences files that could be deleted?

Or perhaps I should delete Lr CC on iMac-2 and reinstall?

[bradleykents]

Thought I should continue to investigate:

I just de-installed Lr CC and chose to not save the preferences.

Restarted iMac-2.

Re-installed Lr CC ... and the same three videos that play on iMac-1 and on my Lr CC online/web app still do not play on iMac-2.

I realized that in Lr CC Preferences>Local Storage>Options, I have checked "Store a copy of all originals at the specified location," so these videos should also be on my hard disk. I located them at the Finder level, and they play both there and when opened in QuickTime, so it seems like the issue has now been pretty much isolated to playback within Lr CC that is not working, but only on iMac-2.

Any thoughts?

[bradleykents]

Actually, I just realized that almost all videos in Lr CC on iMac-2 fail to play ...