48 don't support 4G/LTE.
Only H+ down.
https://community.giffgaff.com/t5/Blog/G-H-E-3G-and-LTE-Making-sense-of-cell-network-alphabet-soup/b...
If you just mean that your data connection is not working then you need to configure your internet settings.
Follow the instructions here
https://community.48months.ie/t5/Other-Help/internet-on-my-phone/m-p/31369#M10212
Hope this helps.
Did that help at all @dave00001?