Divide With a Sum and Filter on same column

fenneran That error indicates you are creating COLUMNS! Convert them to MEASURES!

Try this MEASURE!

It basically just adds zero to the one you've already created but adding zero is by far the easiest way to handle blank in a card!

CallBack =
DIVIDE (
    CALCULATE ( SUM ( 'Raw Calls'[Count] ), 'Raw Calls'[DirectionCode] = FALSE () ),
    CALCULATE ( SUM ( 'Raw Calls'[Count] ), 'Raw Calls'[DirectionCode] = TRUE () ),
    0
)
    + 0

I can't simulate your grouping and filtering but here is what I did:

Using this Enter Data query:

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WSi9KTVfSUTI00AciIwNDMyDHLTGnOBVIGynF6mBXEVJUClJgDFaQlJmTg8sI3CqgRpii22GIbgRuFVAjDA3QLcEww9AQpxKYIUqxsQA=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type text) meta [Serialized.Text = true]) in type table [#"User Name" = _t, Date = _t, Direction = _t, Count = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"User Name", type text}, {"Date", type date}, {"Direction", type logical}, {"Count", Int64.Type}})
in
    #"Changed Type"

I created the following measure that returned the correct result:

CallBack = VAR Incoming = CALCULATE(SUM([Count]),ALL('Raw Calls'),'Raw Calls'[Direction]=FALSE())
VAR Outgoing = CALCULATE(SUM([Count]),ALL('Raw Calls'),'Raw Calls'[Direction]=TRUE())
RETURN Incoming/Outgoing