Is it an iPhone by any chance?
If so it may be this issue due the stupid way that Apple do things:
If it's not an iPhone then you may have to contact 48 support for advice.
Data does not work for some people when roaming in the EU on a Guido membership because the APN field of their settings changes from 48month.liffeytelecom.com but when they edit it to change it back to that, save the changes and reboot it works.
However for some people even doing that doesn't work for some reason and I don't know why 48 support can explain it or fix things so that this does not happen.
Hope this helps.
What networks are listed if you do a manual scan?
Is 48 listed?
If so what happens when you select it?