iPhone 12 Pro / Apple Watch 4 - problems setting up data - 'reference code 10'

[pacpac2020]

Hi, I have a data plan set up on my account. This weekend I set up my new iPhone 12 Pro, configured 'as new' the phone, i.e. without the use of earlier backup. My Apple Watch 4 was also set up fresh and paired to the phone. When in the watch app on the phone I am trying to setup the mobile data app on the watch. When I tap 'Set Up Mobile Data', I get to the O2 screen with the following error message:

'Oops, something went wrong. Try again and if the problem continues call 202 for free from your O2 mobile, quoting reference code 10'

So, cannot get pass this screen to input my username/password to pull down the watch's data configuration. Tried 5-6 times since yesterday, no luck, same error message each time.

Any advice on how I can set up mobile data on my watch? Thanks.

[MI5]

@pacpac2020 

A couple of basic things to check:

1 - software is up to date on both devices.

2 - Watch has been granted access to motion and fitness in phone settings.

Apple may be able to assist if it isn't O2 account related https://www.apple.com/uk/retail/geniusbar/

Alternatively, call call customer service.
Numbers here Guide: Coronavirus Community Help and Support 
Or advice from an O2 Guru regarding a way to get through:
If you call 202, when it comes to the reason you are calling stay silent for 15 seconds and you will be taken to the keypad options.
Press 2 for Everything Else
Press 5 for More Options
Press 7 for Anything Else which will put you though to someone.
Say "Upgrade", "Lost/Stolen" or "Fraud" if you have to, to get put through to someone.

[Marjo]

Hi @pacpac2020  , it would be great to hear how you're getting on with your watch since you last posted. Have you made any progress?

[pacpac2020]

Hi, nope, no luck. Tried resetting the watch a couple of times, still the same error message, unable to log in to O2 to pull the mobile data configuration to the phone. Called customer service and cancelled the mobile data plan.

[Marjo]

Sorry to hear that you had to cancel the plan in the end @pacpac2020 😞