Lately, I am unable to display, when entering edit mode in a cell, the
cell's formula-referenced cells. I used to, upon pressing F2, see a
cell's formula and, highlighted in differing colors, the cells
referenced by the formula to be edited/viewed.

Any ideas how this very useful feature, highlighting the formula's
referenced cells, may be restored? F2 still gets me into edit mode, but
I can no longer see which cells are referenced by the selected cell's
formula.