Parentheses in file name?
A friend of mine using MuseScore 3, installed version, on Windows, was unable to open a file I sent him in email with parentheses (e..g, "(3)") in its name. The file system had no trouble creating it, but the open dialog in MuseScore said "file not found" when he clicked on it. I can't reproduce it because I'm not running Windows. My Mac build has no trouble with it. This happened repeatedly.