The first time this happened to me was when I first got my MTN LTE sim in December 2019 after cellc cancellation.
Nothing worked to fix it, the sim just started working again on its own, day or two later into December.
However it happened today out of the blue, no load shedding required. Axxess support sent me these instructions that worked for me:
Since you've reconfigured the APN settings can you try this troubleshooting one last time:
*Change the network setting to 3G, save and apply.
*Then go to the home page, click on those connection arrows (data traffic arrows)
off and back on
*It will try to connect to 3G, >connecting, connecting, connecting, error - connection failed,profile is invalid.
*Restart your router, leave the network mode on 3G for a few minutes (max 5min) (I waited 10min)
*Click again on the arrows on the home page, off and on, wait again for the error message, then go and change back the network settings : Auto or 4G only.
*Check your status light - should turn blue
and then you should have a connection.
Hope this helps anyone.