After finally manageing to reinstall PowerDVD 12, I have the same issue that prompted me to try update (and which then broke the install)

My primary screen is a 4K, running of an Nvidia GTS 750ti
Up until recently, I've had no trouble playing discs on here.

The two other screens are both HD, running of the internal Intel chip.

However, when I play discs I get a blanks screen (black, or dark purple, or dark blue)
The main screen is large, used for movie watching

I can, howeer, see video on the otehr screens if I move the PowerDVD window

This all started when I tried to play the Atomic Blonde bluray. I assumed it was due to this having a new encryption key, so tried to update the software. Then the application would not start. However, now trying discs I know that worked, I am unable to get any to show on the main screen.

I have sucessfully viewed several films in the past like this, so I am not sure why the current issue.
As for a Windows 10 update, I am running 1903, but can't tell if this updated before or after the troubles started, as I have used a trial version of PowerDVD 19 without any hassles for the last several weeks, while the trial lasted.

Any hints and advice appreciated!