Waiting for the Video Engine to launch

I get this error when trying to enable the video engine in Playback Engine with PT 11.1.2. It shows a progress bar and a message: "Waiting for the Video Engine to launch" and does nothing when it completes. Then I have to hit cancel to continue using PT.
I still have a PT 10.3.7 on the same computer and it works fine with it.

Is there anyone to help me?

Many thanks