Any error messages?
Do you get any signal at all?
Can you scan for networks and see 48 and connect to it?
Are you using an iPhone?
If so then the iPhone may require activation to start working on 48 (blame Apple for this stupid process!),
In that case you need to put a small amount of cash credit on your account because the process will automatically send a UK SMS which costs 25c charged from your credit balance.
Once you have done that switch off and then on again and wait a while - it should activate.
If not then try a sync with iTunes and wait for a bit.
If none of that helps post back with more info and/or contact 48 support:
http://www.48months.ie/help#ask-a-48-agent
Hope this helps.
