Why does Excel MATCH() not find a match?

Functions like MATCH, VLOOKUP and HLOOKUP need to match data type (number or text) whereas COUNTIF/SUMIF make no distinction. Are you using MATCH to find the position or just to establish whether the value exists in your data?

If you have a numeric lookup value you can convert to text in the formula by using &"", e.g.

=MATCH(A1&"",B:B,0)

....or if it's a text lookup value which needs to match with numbers

=MATCH(A1+0,B:B,0)