SPACEBAR does not undo View Entire Map due to design.

Cause:

This behavior is by design of Microsoft Excel. The SPACEBAR key is the shortcut key for the 'View Entire Map' command, but does not act as a toggle to restore the previous view after the entire map is shown.

Solution:

To restore the previous view of a map, select the 'View' menu and select 'Previous', or press CTRL+Y.