You need to have Quicktime installed to play videos.
Please make sure that QuickTime is up to date on your computer
Also uncheck "use graphics processor" under preferences--performance.
Let us know if that helps
Upgrading to the latest QT apple will download didn't help, nor did disabling "use graphics processor". Of interest may be that in grid mode, moving the cursor over a .mov file's thumbnail does scroll through the video (but probably is just single frames rendering without QT).
Here's something that might help...
LR System info hangs after getting to the line "Config.lua flags: None", and displays: "Audio and Video info: Loading" instead of the following text that appears when LR6.1.1 is installed:
Config.lua flags: None
Adapter #1: Vendor : 10de
Device : 11c6
Subsystem : 36523842
Revision : a1
Video Memory : 971
Adapter #2: Vendor : 1414
Device : 8c
Subsystem : 0
Revision : 0
Video Memory : 0
AudioDeviceName: Speakers (Realtek High Definition Audio)
GPUDevice: not available
So it's obviously some sort of adapter problem. Other system info from the dialog that may be useful displays identically on both 6.1.1  and 6.3 :
Operating system: Windows 10
Application architecture: x64
System architecture: x64
Logical processor count: 8
Processor speed: 3.3 GHz
Built-in memory: 12279.1 MB
Real memory available to Lightroom: 12279.1 MB
Real memory used by Lightroom: 548.3 MB (4.4%)
Virtual memory used by Lightroom: 493.5 MB
Memory cache size: 151.0 MB
Maximum thread count used by Camera Raw: 8
Camera Raw SIMD optimization: SSE2
System DPI setting: 96 DPI
Desktop composition enabled: Yes
Displays: 1) 1920x1080, 2) 1920x1080
Input types: Multitouch: No, Integrated touch: No, Integrated pen: No, External touch: No, External pen: No, Keyboard: No
Graphics Processor Info:
GeForce GTX 650 Ti/PCIe/SSE2
Check OpenGL support: Passed
Vendor: NVIDIA Corporation
Version: 3.3.0 NVIDIA 358.91
Renderer: GeForce GTX 650 Ti/PCIe/SSE2
LanguageVersion: 3.30 NVIDIA via Cg compiler
I note you have a NVIDIA GPU there seems to be an issue with the latest update of Windows 10, i.e. to Version 1511 (OS Build 10586.3) that started rolling out last week where the OpenCL (3D Vision Driver) was not updated. (Note if you run Winver from the search box it will provide the version info)
If you have had windows update your PC, download the driver from the NVIDIA website and do a Custom Install choosing to do a Clean Installation (check the "Perform a clean install" box on the Custom Install screen) and that may correct the issue. In my case I checked the GPU using GPU Caps Viewer and noticed there was no OpenCL support so I reinstalled the driver and then I didn't get the symptoms you are getting.
This didn't help. Even reverted back to win8.1 (not voluntarily, goof up thanks to Acronis 2016 Try & Decide killing boot) and it didn't work on 8.1 either. Got the same "Audio and Video info: Loading" sysinfo on 8.1. Another guy on Win10 (dpreview.com) has the same problem. He's got an intel video card (Adobe Lightroom CC 2015.3 and 6.3 arrives with restored import interface and bug fixes: Digital Photography Review)
Thanks for trying to help!
Is anyone else having problems where the playback icons don't show up when loading a .mov file into the loupe?
I have exactly the same symptoms as you, and I know at least one other person that has the same as well. I have an NVidia GPU but there is no difference when I disable it and use the integrated Intel graphics. I did the clean install of the NVidia driver and this did not solve the issue either. I do have Quicktime 7.7.8 where others report this cannot be installed on Win10 but for me it did and runs perfectly (it opens the file that I try to play in Lightroom). Using GPU is unchecked by the way.
In fact, I do have an issue with photoshop as well. When I try to open a video file, it says that "dynamiclink not available". I tried a suggestion in the forum to reinstall iTunes but that didn't work either. I don't know if both issues are related, and I don't know when this started because I never tried videos in photoshop before (just tried it because I found a topic about it when searching for solutions for lightroom).
The other person I mentioned downgraded to 6.1 and the issue disappeared. We both had the problem since 6.2. I haven't done the downgrade yet (kinda "volunteered" to get it solved ).
After also having problems with Photoshop and iCloud for Windows, I decided to start again and reset my windows 10. Now everything installed and is working as expected, all with the latest versions. Don't know if you can do this as well, but it's working for me.
Try the solution in this help article: Lightoom 6.3: After update I can't open any video files. If that doesn't help, then add details about your issue to this topic in the official Adobe feedback forum, where several Adobe product engineers are actively participating: Lightoom 6.3: After update I can't open any video filesAn Adobe engineer in that thread suggests uninstalling and reinstalling LR.
yes me. Also the same issue. Recently update to windows 10 also.