Workfront Fusion Search module Record Type: Project User

Hi,

Screenshots attached......

I'm trying to remove a Project User from a project in the People area, when they are no longer assigned any Tasks.
I'm looking at the object Project User, which I believe is an array of the People on a Project.
When I use the Search module in Workfront, I get an error saying that the object PRTU isn't available even though it's in the module drop down selection.
'[422] PRTU is not a top level object and can't be requested directly in internal'
Has anyone faced this issue?

thanks,

Kelly