New Sim not working

Hello,

I urgently need assistance with a SIM card that has not been working for the past two months.

Background: I was abroad when my phone was stolen. I ordered a replacement SIM and had a friend in the UK ship it to me. Despite following all APN setup instructions, the SIM never connected to any network while I was abroad. I assumed it needed to be activated in the UK first, so I waited to report the issue.

Current situation: I returned to the UK today and the SIM still will not connect. My phone can detect the SMARTY 3G and 4G networks in the settings, but when I attempt to connect, I receive the error message "couldn't connect to the network."

Could you please help me resolve this issue as soon as possible? I've been without mobile service for two months and need to get this working urgently.

Many thanks for your assistance.

Best regards, Fran