windows Nokia phone data connection not working

[bbdd]

Nokia Lumia 650. Giffgaff / O2 network in the UK. There was a power cut yesterday, power came back on. Phone/data/internet working fine before power cut. I use the phone to give my laptop an internet connection via hotspot. So later, tried to connect back to the internet. Couldn't. Couldn't get the hotspot to work. I now realise the phone's data isn't working, trying to use the phone's browser results in "You're not connected". The phone itself as a phone is working, but not the data. I've checked my Giffgaff account online and that seems fine. I've travelled somewhere else, well away from where the power cut was, and the same situation persists on the phone: Phone works, no data, no data connection. In the settings, "Mobile data" is "on". Any ideas what's going on? How to fix? Thanks.

 

[bbdd]

I worked it out. For the record:

On the SIM info control panel there's a "Internet APN" section near the bottom.

I added a new Internet APN using some of the info from here https://www.giffgaff.com/help/articles/internet-apn-settings-guide

and then it worked again.