Conditional Formatting Won't Highlight Rows

I've been trying to highlight rows green when one of the cell values in that row is "TRUE" (linked to a checkbox), using conditional formatting. I've looked at over 10 tutorials, yet nothing happens when I enter the formula: =$I4="TRUE" (and I am changing the format to green). I highlighted the cells and I've also tried the formula for D3, I3, A3, and A1 in case it was being weird about selecting a certain cell. But alas, there are no highlights.

I even followed one of the tutorials exactly; I recreated their chart in a new workbook with the same values in the same cells. I highlighted the cells they did and copy-pasted their formula.

Nothing.

I don't know what I'm doing wrong or if this is a problem with Excel itself. I've attached a sample; any tips?