Keep in mind this was three years ago. I have had the same issue today.

https://community.48.ie/t5/Phones/Text-Messages-nightmare/td-p/57213

I thought it was an issue with my phone as I have an iPhone 12 Pro Max so I restarted my phone, toggled airplane mode on and off. Turned of iMessages and turned it back on. Didn't work.

Turns out that 48 does not support receiving or sending text messages to premium SMS short code numbers like 50123, or 50840.

It also happened when I tried to send a message to the HSE short code premium number to register for quick emergency text them in case of an emergency. 

It also happened yesterday when I was trying to receive a verification code from Kaggle and NVIDIA for a conference.

I contacted the useless chat support and they were no help. Like the initial poster said before there is no quick fix. They said they were still working to expand their services, but you can guess how true that is when this exact issue happened in 2022 and there has been no change.

The solution: Quit 48 and move to a different service provider.