IF= Function not recognizing defined name.

You need to put quotes around the text you want to display.
Without the quotes, Excel tries to find a defined name with that text and returns an error.

Try this:

F2: =IF(OR(C2={"AAB","AAF","AAJ","AAL","AAS","AAX","LON","OFF"})
,"BNYM EMEA Tax and Documentation","Enter Contact")

Does that help?