SSAS Live Connection with SWITCH statements

I am trying to create a disconnected slicer with the combination of Power BI and SSAS Live connection.  My measure looks something like this:

=SWITCH(TRUE()
,SELECTEDVALUE(UOM[UOM])="Cases",'Metrics Demand Plan'[ISS_CASE_AMT]
,SELECTEDVALUE(UOM[UOM])="Pounds",'Metrics Demand Plan'[ISS_POUND_AMT]
,SELECTEDVALUE(UOM[UOM])="Gallons",'Metrics Demand Plan'[ISS_GAL_AMT]
,SELECTEDVALUE(UOM[UOM])="Eaches",'Metrics Demand Plan'[ISS_EACH_AMT]
,SELECTEDVALUE(UOM[UOM])="Pallets",'Metrics Demand Plan'[ISS_PAL_AMT]
,SELECTEDVALUE(UOM[UOM])="Dozens",'Metrics Demand Plan'[ISS_DOZ_AMT]
)

That seems to work fine in Power BI with an imported data source.  However, it does not seem to work when I put the same formula in a SSAS tabular model and try to use it with a live connection.  My assumption was that DAX would work fine regardless of what sources I was using and I assumed that the Tabular model for SSAS would work the same as the model in Power BI.  Is there something I'm doing wrong?  Or is this not possible?