A7 Lite - Problems setting up Three prepaid sim

[Wightknight]

I have just bought a Galaxy A7 Lite LTE and want to install a sim card. I have bought a Three 24GB Pay As you Go Data SIM Card which is a sim card preloaded with data.

My tablet will not recognise that the sim card is installed, so I cannot turn on mobile data and it doesn't appear anywhere in the settings.

To check that the tablet isn't faulty, I put a standard Three PAYG sim from a mobile phone in the tablet. It works perfectly.

Has anyone else used one of these Three data sims? Any advice you have will be gratefully received.