Cannot expand hidden rows in excel Office 365 for Mac!

I have downloaded an excel file to my Mac where many columns and rows are hidden. I want to expand them but when I mark the rows before and after the "dubbel line" with hidden rows and then right clic on "expand rows" nothing happens.

The excel sheet is not looked since I can open the rows one by one by dragging one line at the time down wards, but it takes for ever to open them one by one - very timne consuming....

What should I do to unlock the hidden rows???