I accidentally deleted a Libreoffice spreadsheet I was working on, so I went to fetch a backup from Time Machine on my iMac. The file folder was there, but it wouldn’t open. I checked some other spreadsheets, and was amazed to find that none of them would open! (They just showed a generic blank-folder image.) Time Machine seems to work with all my other apps, but it won’t open anything in Libreoffice.