Same as Dubcat. Must be the new inside and outside option in Coronas AO map.
>>> SCENE Info: <<<
Corona version: 1.5 DailyBuild Aug 25 2016, build timestamp: Aug 25 2016 21:31:47
Converter version: 1.27
Installed Vray plugins: V_Ray_RT_3_20_03 V_Ray_Adv_3_20_03
# Material conversion took 0.006 seconds
# Iterations: 0, converted: 0
# Map conversion took 0.009 seconds
# Iterations: 2, converted: 0
# Light conversion took 0.001 seconds
# Iterations: 0
Error occured in VRayDirt : Map #4240:VRayDirt
-- Unknown property: "invert" in Map #4240:CoronaAO
Error occured in VRayDirt : Map #4240:VRayDirt
-- Unknown property: "invert" in Map #4240:CoronaAO