Unable to use GPS or Data Roaming in order to get Directions

Hello there,
Before departing Australia I made a point of setting up an account that enables me to use unlimited data. I did this in case GPS failed. While wandering the streets of Rome GPS has let me down – it simply won’t function. I then turn the iPad onto mobile roaming but I am still unable to put in an address and plan a route because it says ‘I require wifi’. I would appreciate any advice you can give to placate the problem – thank you.