Did anything change on your phone?
Software update or settings changes etc.?
Are your internet settings still configured correctly?
Maybe delete the current APN and reconfigure them from scratch to see if that helps?
https://community.48months.ie/t5/The-Knowledgebase/My-Internet-is-not-working/ta-p/45928If none of that helps then you may need to contact 48 support for more assistance.
See the link in my signature below.
Hope this helps.