Every time I save a spreadsheet and sometimes on other operations I get a “not responding” message. Can anyone explain why?
As you give really not much information only guessing possible. Maybe some security system of your unknown OS interferes with saving.
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Typical stuff: MacOS, but no full disk access, AntiVirus software wich does not know of the newly installed software. CloudStorage not accessible.
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One of my first point to analyze would be, if it is only spreadsheets or also Writer-documents affected or you could save in Excel format .xlsx
You probably save early, save often and keep proper backups. If that is the case, then turn off auto backups, on big files they do cause unexpected delays