Ste,
Is this a new iphone that you transferred data onto from your old phone? If so, what process did you use to transfer data from the old phone to the new phone? Did you use iTunes or iCloud? It may be that you did not transfer the data necessary to decrypt games saved on your old phone. In order to open games saved on another phone, your new phone would need the old phone’s keychain data. Depending on how you performed the transfer, this may not have happened.
Thanks for playing!
Amon