Conditional formatting not working properly as one of the comparing cells contains a vlookup formula

Hi Odin,

Conditional formatting, as any other formatting, definitely doesn't depend on how the cell receives its value, by formula or it was entered manually.

However, the formula could return not what we assume (e.g. text with some non-visible characters).

Another point is formatting. It looks like on your first screenshot both columns are formatted as text (green triangle on top left of each cell). For the next screenshot second column is not text (otherwise formula doesn't work) and you compare text in first column with number in second one.

That could be something else, without sample file attached with non-sensitive information we may discuss forever what could be possible reasons. But you my try one by one, start from Wyn's suggestion, most probably it works.