Difference between 'Open', 'Select' and 'Expand'
 

When trying to open .xlsx files that is shown in file list, I get drop-down
box that shows one of above commands. 'Open' persistently does not work:
gives 'Cannot find file etc..', other two do but do not always appear.
How can I repair 'Open' or get 'Select' or 'Expand' to appear?