On musescore: You will see your name in the top right-hand corner of this browser window. Click on it and select "My scores".
If your score has been saved there, you will find it. If it's not there, you haven't saved it in the musescore cloud.
Click on "Download". The file will be opened automatically by musescore, but it will also be saved in the download folder.
And in MuS4 you can open it directly from the program - as far as I know. (I do not use MuS4).
But that seems to be your problem right now ...
Comments
Which cloud? musescore.com or Dropbox or another?
On musescore: You will see your name in the top right-hand corner of this browser window. Click on it and select "My scores".
If your score has been saved there, you will find it. If it's not there, you haven't saved it in the musescore cloud.
Click on "Download". The file will be opened automatically by musescore, but it will also be saved in the download folder.
And in MuS4 you can open it directly from the program - as far as I know. (I do not use MuS4).
But that seems to be your problem right now ...
See:
https://musescore.org/en/handbook/4/opening-and-saving-scores#Overview