Default Game backup doesn't work after changing ROM

I've recently flashed a new version of my current ROM and although Real Racing works like a champ after restoring my Titanium backup, NFS Most Wanted won't play ball. When I try to launch the app I get the message "NFS is not authorised for this Android device, and it immediately closes. Going to the Play Store whilst logged into the same Google account I purchased the game with shows me NFS as if I had not purchased.

Restoring my nandroid of the earlier ROM allows me to go to the Play Store (logged in with the exact same Google account) and NFS MW shows as purchased.

Presumably this is to do with device ID, perhaps? Can anyone explain, please?

EDIT:
Resolved by restoring nandroid where game worked, flashing new ROM from scratch and restoring Android ID from old nandroid when asked by Titanium if I wanted to keep new ID or restore old Android ID.
--------------------------------------
MY LATEST HONEY
Phone :: Google Nexus 5
ROM :: Mahdi-ROM 2.5
Kernel: Mahdi

BITCH, I JUST DON'T LOVE YOU NO MORE
Phone :: Samsung Galaxy S3 i9300
ROM :: CM10.1
Kernel: Boeffla

RETIRED / SOLD / STOPPED WORKING
Phone :: HTC Desire Z, HTC Desire, TMobile G1

BRIEFLY FLIRTED WITH
Phone :: Google Nexus 4, Samsung Galaxy S i9000, Google Nexus 1