Problem: Can't add a split pane to split the window. When you drag the split pane tool into position, then release the mouse button, nothing happens.
Solution:
Are you trying to add a third split pane in that direction?
The maximum number of split panes in each direction is two (i.e., two horizontal and two vertical split panes).
Are you trying to add a second split pane in that direction?
When adding a second vertical split pane, the second one must be added to the left of the first. When adding a second horizontal split pane, the second one must be added above the first.
Are you trying to add the first split pane in in that direction?
The spreadsheet may already have a split pane at the extreme left or top of the spreadsheet that may not be readily visible. To test for this, first scroll the window to the home position (cell A1 at the upper left corner of the window).
For a horizontal split pane: Place the mouse pointer over one of the row numbers. Slowly move the mouse into column A. If the mouse pointer changes shape to the double-arrow, you've located the existing vertical pane tool. Using the mouse, drag the split pane to the desired window location.
For a vertical split pane: Place the mouse pointer over one of the column letters. Slowly move the mouse down into row 1.
If the mouse pointer changes shape to the double-arrow, you've located the existing horizontal pane tool. Using the mouse, drag the split pane to the desired window location.