DAX expression I cannot get to work - please help.

Here's what worked but I don't understand why!

I just added the red part and all worked.

% of Premium = DIVIDE(SUM('Agency Scorecard 3'[Earned Premium]), CALCULATE(SUM('Agency Scorecard 3'[Earned Premium]), ALLEXCEPT('Agency Scorecard 3','Agency Scorecard 3'[Loss Year]),'Agency Scorecard 3'[Summary Line ID],'Business Division'[BusinessDivisionID], VALUES('Business Division'[BusinessDivisionID])), 0)

Thanks all for your help in getting me on the right track.

Here's the post that explains why the Values function works so now I know.

https://community.powerbi.com/t5/Desktop/ALLEXCEPT-only-working-on-visible-row-context/td-p/18030

You keep adding for all your report (might work with page/visualisation filters I don;t know) filters as follows:

% of Premium = DIVIDE(SUM('Agency Scorecard 3'[Earned Premium]), CALCULATE( SUM('Agency Scorecard 3'[Earned Premium]), ALLEXCEPT('Agency Scorecard 3','Agency Scorecard 3'[Loss Year]),'Agency Scorecard 3'[Summary Line ID],'Business Division'[BusinessDivisionID], VALUES('Business Division'[BusinessDivisionID]), VALUES('Agent'[Agent Alternate 1]), VALUES('Agent'[Agent Alternate 2]), VALUES('Sub Producer'[Alt Sub Producer 2]), VALUES('Managing Unit'[Managing Unit Name]), VALUES(Office[Office]), VALUES('Product Line'[Product Line Name]), VALUES(Underwriter[Underwriter Name]) ),0)