Thanks for the good, clear guidance guys, I really appreciate it.
So, I went to try the suggestion by vpeter, to see if I could connect from a browser on my phone.
I could connect from my phone. But today Kore works as well. I have no idea why. Didn't change anything. But today it works.
If I get a repeat of the problem I'll do as Iridium describes, and collect the logs.
Thanks again.