I have the following formula in cell R5:
=SUMPRODUCT((I4:N28)*(B4:B28=R3)*(I1:N1="*"&R4&"*"))
I would expect it to return 120 but returns 0. It transpires I can not use wildcard in sumproduct() like I typically would with sumif(). Any help on incorporating a wildcard into sumproduct() is appreciated.
Many thanks, Alan.

Try using the following formula which uses
SEARCH()Function.Another alternative way: