Thanks David, for getting back to me.
None of this explains why it ran for a week or two and then stopped.
Its my own virtual server and its not shared. I have had two other sites on it in the past but they are now defunct.
I am/was tracking about 15 keywords.
There is only one site on my IP address (18.104.22.168) and it is my own IP address, so that's not what the problem is.
I could easily switch hosts in an hour or so, but I don't think that's what needs to happen here, David.
The site is behind the Cloud Flare firewall. Can you give me enough technical details that I can check with them that they are not blocking access for some reason.
Other than that, any ideas?