Working fine for me in Dublin (city centre).
Have you tried the usual stuff - switching off, taking the SIM out, cleaning it, reseating it, switching on, manually scanning for networks and connecting to 48 afresh etc.? Check that your settings are still correct (in particular roaming is enabled).
If that doesn't help then you'll probably have to contact 48 support:
http://help.48months.ie/hc/en-us/requests/new
Hope this helps.
