what she meant by that is that the test you're using is Case Sensitive.
Meaning that it will ONLY match if it is EXACTLY as you've listed it.
If you use instead:

ucase(sheets("Mary").range("I" & row).value) = "BIGSUPPLIER"
then whatever is in the cell will be forced to upper case before
comparing it to the name (you have to be sure and write the name in CAPS!)