Attempting to use an IF VLOOKUP in a conditional formatting formula and getting invalid formula

I've got a list of data validated options that pull from another sheet in the spreadsheet (e.g. a list of options on a hidden sheet to make the drop down menu nice and neat) and I want to conditionally uncover checkboxes for options on the list that need them, but the conditional formatting doesn't like my IF VLOOKUP to uncover the square.

Right now I have it so the square is by default background colored black with the 'text' in the box black too, so the checkboxes are hidden. If you select an option with a checkbox needed, I want the formatting to clear (white background, normal text) so you see the checkbox as intended.

I've tried a few google searches but nothing seemed to clear it up for me.

=IFERROR(IF(VLOOKUP(A42,'Mastery Data Table'!$A$25:$D$156,3,FALSE)=1,TRUE,FALSE),FALSE)

I'm using IFERROR because some options have no data in column 3 at all.