Cannot connect Apple Watch

[ziss1971]

A previously paired and mobile data connected watch will now not connect. Both phone and watch have been reset multiple times, all caches cleared and password for the account is simple and lower case only.

However every time I try to add mobile data i get an error that states simple There is a problem. 

Any advice (that does not involve blaming this on Apple or suggest that I reset the devices) would be appreciated

I have a screen shot but it is simply: the 3 logo, a red triangle with a banner There is a problem. Under that is a description that reads - There is a problem and a button to Close

[cvnvr]

If you haven't already seen, there is a large existing thread with many users having similar issues: https://community.three.co.uk/t5/Devices/Apple-Watch-pairing-error/td-p/5827

Don't have much advice as I'm still trying to resolve the same thing. After several weeks and many phone calls, nothing yet.