Slice expression not limiting records when selecting from a different table

[tjwnc]

I created a slice for parent table Parks to limit the list of Parks to only those not already selected by a user.
Parent table PARKS has field NAME
Child table USER PARKS has reference field PARK back to PARKS.NAME

This expression doe not limit the rows:
NOT(IN([Name], SELECT(User Parks[Park], [User Email] = USEREMAIL())))

As a test this hard coded expression will work and limit rows, excluding 'Carrier Park' 
NOT([Name]= "Carrier Park")

This hardcoded expression back to User Parks does not limit the rows either, 'Carrier Park' included in the list :
NOT(IN([Name], SELECT(User Parks[Park], [Park] = "Carrier Park")))

Thank you for any assistance.