Hello,
I am rendering in 8k for the first time.
I have rendered multiple times with similar results.
One example is that the file shows in windows explorer as 426mb in size, but .01 sec in length.
Sometimes the file has a thumbnail, other times not. 
I have tried a few different video players and can't play it back.
I have tried it in the default Windows media player (Win 10) Quick Time, VLC all with no luck


any suggestions?

thanks,
Malcolm Park

Which Video Format are you using?
I suspect that the rendering might have failed. 426mb seems to be pretty small.
I've just made a test with 8K Prores, High Quality, 422 as well as 8K Prores UHQ, 444 and both played in MPC-Player (recommended on Windows, it's the fastest and the best http://mpc-hc.org/ - please get rid of Quicktime, VLC got worse and worse too over the last years.)

Of course those 8K Videos do not play in real time on my hardware, but I didn't expect that. Current hardware sometimes even struggles playing back 4K stuff in the quality the LRT delivers. Those are master files meant for further processing in a video editor.
For direct playback I always recommend rendering a Full HD or 3K MP4, it's much leaner.

BTW: Explorer shows the duration correctly too for my 8k renders.

Please render again, then send me the log file after rendering (info menu).

thanks Gunther,
I re-ran the rendering process and I found the right combination of settings to get a good output file.
X_ProRes-422_8KUHD_29.97_HQ.mov is 4.98gb in size.
I downloaded and installed MPC-Player which opened the file as you said it would.
The playback is slow as you say, but at least I can see what it looks like.
Thanks as always,
Malcolm

One more question if I may. Shooting with a 36mp Nikon D810a and rendering in 8K, do you see any loss or distortion as the sensor is only 95.83% of 8k

No, the video will get scaled up a bit, but that's not a problem.

thanks