My Sketchup Pro 2021 Version 21.1.298 is not saving my work.
I work on a project, have autosave on, and save manually, but when I reopen the file it’s at the same state as earlier.
I tried an experiment. The file was last opened yesterday 3 September. Opened it today and added a series of shapes, saved it, and then reopened. Nothing new there, and the ‘Get Info’ panel said it hadn’t been modifies since yesterday.
Autosave is saving a recovery version of the file, which is deeply buried in the application support folder. It won’t affect your test.
Manual saves should be working, but you could double check where the file is, in case you’re working on a different file than you think you are. If you Command-click on the document’s title, you will see the full path to where the file is. See if it’s where you think it was.
Make sure not to work directly from an iCloud Drive folder. There may be synching going on that is reseting the file to the state it is in on another machine.