This is the spreadsheet I'm working on. I am trying to figure out a formula for conditional formatting so that it only highlights the cells in red if none of the cells from columns N to Y of the Failed tab says either "Yes, I take this medication within the specified dosage range" or "I am unsure If I take this".
After selecting the range N2:Y, apply to it conditional formatting with "Custom formula is:"
=sum(arrayformula(n(regexmatch($N2:$Y2, "Yes, I take this medication within the specified dosage range|I am unsure If I take this")))) = 0
$N2:$Y2 refers to the range N-Y in the current row.
regexmatch($N2:$Y2, "this|that") returns True when the cell contains either "this" or "that" (this is a substring search, which is appropriate in your case). Then
N converts True to 1 and False to 0. The whole array of these 1-0 values is then summed, and the formatting applies if the sum is 0, meaning there were no matches.