sim is not provisioned

[KT6]

I received a new sim on Saturday in an o2 store after losing my phone the previous day. It took nearly 24 for to activate. Afterward it has been working well. Today it has stopped working and says  ' sim not provisioned '

[pgn]

Did you report the phone you lost to O2, @KT6?

Guide: Lost or Stolen O2 Device? - How to Report it 

That would have triggered O2 to disable your old SIM and send you a replacement.

Failing that, as we cannot access your account here, it's a call to O2 on one of the numbers in this Guide: Coronavirus Community Help and Support or via Social Media, links below. Good luck!