Were you rendering in 4K ?
I have seen the problem as well where PowerDirector is rendering files that seem to have audio only.
I was not using HEVC though, plain old H.264, in M2TS files.
This seems to happen most often when rendering at 4K resolution, when using the hardware accelerator on my nVidia card (a GTX 750). I didn't try the software encoder as the rendering would take about 6 hours.
Right now, I have a project that reproduces the issue.
PD generated a 20 minute, 4GB file in UHD H.264, which took 1h20 to render.
And then, it can only play the audio in it. It's clear there is more than audio inside. It's an encoding issue.
PowerDVD also can't play the video part of it.
The project is too large to upload for a test case though. I will try to reduce the size and file yet another bug report with Cyberlink.
MSI X99A Raider
Intel i7-5820k @ 4.4 GHz
32GB DDR4 RAM
Gigabyte nVidia GTX 960 4GB
480 GB Patriot Ignite SSD (boot)
2 x 480 GB Sandisk Ultra II SSD (striped)
6 x 1 TB Samsung 860 SSD (striped)
2 x LG 32UD59-B 32" 4K
Asus PB238 23" HD (portrait)