One of my Scores is not opening…

Well, no one can get your file back from a screenshot of the error message!
Search in these (partly hidden) folders for the file:

C:\Users\{YourUserAccount}\AppData\Local\MuseScore\MuseScore4
C:\Users\{YourUserAccount}\AppData\Local\MuseScore\MuseScore4\cloud_scores
C:\Users\{YourUserAccount}\AppData\Local\MuseScore\MuseScore4\cloud_scores\.mscbackup
C:\Users\{YourUserAccount}\Documents\MuseScore4\Scores
C:\Users\{YourUserAccount}\Documents\MuseScore4\Scores\.mscbackup
C:\Users\{YourUserAccount}\Documents\MuseScore4\Cloud_Scores

And for the future: Save the score locally and only as a backup in the cloud!