As others here have mentioned, DLC can confuse things. The pass is connected to the Box (i.e. your PlayStation) it would seem. If you have another account, login with that, fire up ME3, it will ask you to login or create EA account, then you can proceed to Online pass. Select purchase and you will be able to purchase one for Free. once downloaded and activated you will see the main menu has altered to reflect your access to online gaming. logout, login with your main and you should find you can immediately start multiplayer.
P.S, yes I realise the time delay for my response, just thought I'd leave this here for others who might have this issue
