Perhaps your regional settings require semi-colon separators rather than commas.
Assuming your data in two adjacent cells in the same row (like A1:B1 as per your example) this formula might also work for you
=TEXT(DOLLARFR(SUMPRODUCT(MID(0&A1:B1,FIND({"Y";"M"},0&A1:B1)-3,2)*{12,-12;1,-1})/12,12)*100,"##"" Y - ""00"" M""")
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