SELECTEDVALUE doesn't work

I am trying to use the the SELECTEDVALUE function like this:

Selected ASM = SELECTEDVALUE(MBO_PC_HEALTH_CHECK[SLS_MGR_NAME],"more than one")

When I select a single SLS_MGR_NAME in a slicer it says there is more than one selected value.  As a test I put the "Selected ASM" and SLS_MGR_NAME columns in a table visual.  The SLS_MGR_NAME column correctly displays the one selected value while the SELECTED ASM columns shows "more than one".