Are you clicking the cell that you are trying to link to twice?
If you enter = in a cell in one pane and then click a cell in the other pane, the first click simply puts the focus on the other pane but doesn't actually select the cell.
The only change I notice after the first click is that the Excel symbol next to the title of the pane (e.g. Book1:1) moves from the pane where I entered the = in to the pane I just clicked on. Only after I click the cell again does the cell reference appear in the original cell.
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