2 matrix tables each with slicers - 3rd table that does a calculation

Hi rayonlinenz ,

In DAX, you can’t aggregate an entire table directly.
For example, this is invalid: Left Score = SUM(Append1)

Functions such as SUM, COUNT, and similar must always reference a column, not a table. Because of this, the error you’re seeing is not related to Append1 being an appended table appended tables behave the same as any other table in DAX.

Correct approach for the Left Score measure

Left Score :=
CALCULATE (
COUNT ( Append1[Event_Number] ),
ALL ( Append1_disconnect )
)

This ensures the measure respects the left-side slicers and matrix context while ignoring filters from the disconnected right-side table.

Hope this helps.
Thank you.