Unable to perform a join on delta table with Hash value

Question

Delta Table A : Member

MemberID , FirstName , HashFN 1 ABC bzh7IbKC0CEqmrPLMY/ExQ==

Delta Table B : MemberHashh

CustomerID , FirstName , HashFN 1 EFG bzh7IbKC0CEqmrPLMY/ExQ==

I have to perform join on delta table on HashFN column

Merge Into MemberHashh T1 Using Membership T2 On T2.HashedFistName == T1.HashFN when Matched then Update Set t1.FirstName=t2.FirstName

I'm using Merge however the update is not happening.

Can anyone suggest how to perform join on Hash values