Look in Reliability History and Event Viewer for any error codes, warnings, or even informational events that you can associate with DaVinci Resolve's stoppage.
Reliability History provides a timeline format so any issues likely will begin at or just after you installed the preview.
That said, remember that Windows 11 is a preview. And installed software and drivers are indeed likely to stop or otherwise not work as before.
It may start working "tomorrow" after some fix or update either by Microsoft and/or DaVinci Resolve.
And something else will stop or otherwise not work correctly.
What you should do is just keep trying things and looking. Keep notes.
You may discover some fix yourself or someone else could do so and post accordingly.
All "fixes" may not be the same......