Can't manually adjust panes

[nbarman2022]

Hi - I just installed Sliding Panes for the first time and while everything seems to be working correctly, I am not able to manually increase or decrease the width of an open pane. When I hover over the left edge of a pane, the edge becomes prominent and the mouse pointer changes to the dragging pointer (vertical line with right and left arrows beside it), but I cannot actually drag the panes to become wider or narrower.

Please help!