I have been a semi user of PowerDVD since version 16, upgraded to 17 and found that version 17 didn't play DVDs from the computer to the TV using Chromecast. Which is why I bought it in the first place, the literature is very vague as I'm sure you are aware. I also had problems playing MP4 video files to a TV using Chromecast, this sometimes worked and sometimes it didn't, very frustrating.
I recently as in "today" upgraded to PowerDVD 19 in the hope that simply being able to play an MP4 file to a Chromecast had been improved and was bullet proof. But NO, I still can't play an MP4 video file to a Chromecast device, which if I go back far enough in time was all I really wanted to do.
There appears to be no "fix" coming for the problem and no real guidance from Cyberlink apart from "Call Google", which is a poor get out for a badly designed product.