IM508 failed to communicate if use manual selection (Subaru->Manual selection-> America->Outback -> 2013-2020 -> Blade Key-> With Immobilizer ECU-> Control unit-> Immobilizer (CAN)->Add key ).
I tested working by selecting from system.
Go to System selection-> Immobilizer->Auto identify->Immobilizer remote control learning->Add key
Insert learnt key (working key) and turn on the ignition
Insert new key to be programmed and turn on ignition
Key learning successful.
Test the new key and remote control.
Done.
Program Subaru Outback 2018 Blade Key with Autel IM508