Preview not working when cut, trim.

I assume you mean that whenever you're adjust the in/out points of a clip in the timeline, you don't see the smaller in/out points shown in the Program viewer as per usual? Because that same problem is happening to me. I have a project, and if I open it in the release version of PPro, (24.2.1 Build 2), if I drag the in or out point of a clip in my timeline, or use Y to slip/slide it, I see the in/out frames appear in my Program monitor as usual. If I open the same project in the latest beta version (24.4.0 Build 13), I never see the in/out frames in the Program monitor, I just see whatever frame happens to be under the playhead.

I'm on Windows 10, on Nvidia 551.61 drivers; I will update now to 551.76 to see if that makes any difference (I doubt it will).

...Nope, updating to the latest drivers made no difference.