Mass Effect 3: PS3 DLC & Online Pass Not Recognised

Hi everybody,

I bought an online pass and some DLC (the two weapon packs, Firefight & Groundwar, and that Genesis 2 comic) today through PSN and installed them to the HDD. Problem is, the game doesn't seem to acknowledge that they've been installed. Whenever I try to access the multiplayer I'm prompted to buy a pass or redeem a code, with the 'buy a pass' option causing an error that returns me to the main menu. The DLC packs aren't working either. I've tried reinstalling and restarting the machine on the advice I've found on other forums but nothing's worked so far. Does anyone know what causes this issue and what the fixes/work-arounds are?

Thanks in advance.