When I open an open office spreadsheet that has several tabs, I only am able to see/use one tab, no others appear? Can I fix that?

Once possibility is that you’ve hidden those sheets and there’s an easy fix for that. Select Format. You’ll get a drop-down menu from which you’ll need to select Sheet. If you have any hidden tabs, you’ll have the option to Show. Select Show and you should be able to see your sheet.

~ Cynthia