old Musescore files not playing in Musescore 4 and Musescore 3 not there.

My old files from Musescore 3 are opening in Musescore 4, but there is no sound on playback. Contrary to https://musescore.org/en/node/339915 there is no speaker icon on the task bar for me to investigate the properties. I know the playback is working because there is sound when I create a new file on Musescore 4. How do I get my old files to play?
Or
Please can I download Musescore 3? When I went to https://musescore.org/en/3.0 to do this, the actual download was Musescore 4 again!