Make sure your Propeller is in a Set and use that Set in VSPAERO (either thick or thin -- start with thin). You can't get away with using the 'Shown' set for propellers with VSPAERO.
Then put the Propeller into either 'Blades' or 'Disk' mode.
If you use Disk, then the Disk tab will be active in the VSPAERO GUI.
If you use Blades, then go to the 'Advanced' tab in VSPAERO. There is a pull-down to set the Propeller mode -- 'Static Blades', 'Unsteady Rotating', or 'Pseudo Steady Rotating'. Choose one of the rotating blade choices.
Then the Propeller tab should become active.
Rob