Your only choice is to start proceeding at NCAT against him personally because only the EC or Strata can issue a Notice to Comply.
This involves going to conciliation and then adjudication and cost around $200. It doesn’t matter who owns the car just that it is driven by an occupier who stays overnight on a regular basis.
Take photos (date stamped if possible) of the car in the Visitor parking bay and parked outside over a 7 day period and then randomly to show it’s not an isolated incident. If you can obtain a photo of him getting out of the drivers seat even better.