How do i add a sheet to my Calc ods

I originally created this “database” on some excel editor. Since I have opened it with openoffice and LibreOffice but can’t add sheets to it. Can’t add a sheet, can’t insert a sheet… In libreoffice I hit the “+” button to the left of the 3 named sheet labels and nothing happens.

I can edit the document, it isn’t in read only. I can edit the doc in every other way, so it isn’t protected. I was looking up similar problems other have had, and the “record changes” under “edit” is unchecked.

Why can’t I do something as easy as adding another sheet???

(I am using windows 8.1 and have LibreOffice 5.0 installed and am working with a calc document in English)