USERID2 as USERID
where not Exists(USERID, USERID2)
When a USERID2 value is found that doesn't exist in the excel file then you add it as USERID. Then it exists as USERID. So any other records with the same USERID2 value are skipped.
That doesn't explain why no records are loaded from the qvd file though. Perhaps there are no records that don't have A as userbusinessunit.