Recently, an upgrade in the Australian ATC systems means the use of RMK/GPSRNAV has been deprecated and now is ignored when you submit a flight plan.
If you were qualified as such, now you need to ensure you submit a plan with the following avionics;
and use the following PBN codes;
C2 O2 S1
To change this in AvPlan EFB, tap Settings, Aircraft Type Database, Your Aircraft Type, Your call sign.