Index match array return all matching values

I have this Index Match array formula that returns corresponding values from a matrix {=INDEX($A$2:$A$412,MATCH(1,MMULT(--($B$2:$R$412=A5),TRANSPOSE(COLUMN($B$2:$R$412)^0)),0))} which works fine, however it only returns the first matching value from the data and not all matching values, how could I amend it to return any and all matching values rather than just stopping at the first match. Oh, I also wanted to add and IFERROR of 'Not Found' but couldn't get the parentheses correct, but that isn't vital.

Thanks