Updating query not pulling any records.

Hi, all I am using an Update query which should update the total columns of the table based on the spread sheet values given by where condition. i have pulled that spread sheet results to a table and joined the these two tables in my update query, but it is not updating any records, its always showing 0 records affected. This is my update query, can anyone help me in this.

Query:

Update dbo.Update1 

Set [SubSystemName] = b.[SubSystemName],
[PROV_TAX_ID] = b.[PROV_TAX_ID],
[Updated Bucket] = b.[Updated Bucket],
[Prov_Type] = b.[Prov_Type],
[Act_SQS_Amt]=b.[Act_SQS_Amt],
[Deal_Name]= b.[Deal_Name],
[TINs Provided by:] = b.[TINs Provided by:],
[Other name] = b.[Other name],
[Objector?] = b.[Objector?],
[IPA_Ind]= b.[IPA_Ind],
[Phys_Hosp_Ind]= b.[Phys_Hosp_Ind],
[Settlement_ID] = b.[Settlement_ID],
[Minimum Objection Date]= b.[Minimum Objection Date],
[Comments]=b.[Comments],
[Date added]= b.[Date added]
From dbo.Update1 a
Join dbo.Update2 b
on a.PROV_TAX_ID = b.Prov_Tax_ID
where a.PROV_TAX_ID = b.Prov_Tax_ID
AND   a.Prov_Type = b.Prov_Type