Was it ever working ok?
Are you sure that your internet/APN settings are correct?
https://community.48.ie/t5/The-Knowledgebase/Data-APN-Settings-i-e-Internet-amp-MMS-Settings/ta-p/53...Try running a few speed tests using the Ookla app and post the results.
Where are you located?
Have you tried contacting 48 support about this?
Hope this helps.
