This is similar to the issue reported by Pat. Host has issues contacting the intermediary server due to some network problems either on the Host computer or the network. Also, this might be firewall activity on the same pc or in-between.
I do not have any other hosts to compare, but this does happen with multiple viewers coming in from different networks.
That might point at connectivity issues on the Host side which is also confirmed by the Host log you are referring to. Socket error #11001 may be caused by plenty of reasons, and generally it's connectivity/network issues between Host PC and remote server (in this case - our public server).
I don't think it is a DNS lookup issue since it does work intermittently.
It would be error #11004 then.
Have there been any other reports of difficulty communicating with the ID servers?
No, the servers are up and running. No recent maintenance or downtimes.
I would recommend that you check the firewall and antivirus software on your Host PC. For Internet-ID connection to work only outbound connection to our server is required, and such connection is normally allowed by default in modern firewalls , but who knows if there is any special policy or filter in place.
As for antivirus software, you could add Host's installation path to its exceptions list. You can do so with any a/v software including Microsoft's Windows Defender if that is what is being used on that computer.
May I ask if you are the only user who works with the address book file at a time (from different Viewer machines)? If there are multiple users, a conflict may occur in which case it would be best to use a more advanced address book synchronization available in our self-hosted server.
If you can connect and only occasionally have disconnects, that might point at possible network connectivity issues. Brief network disruptions (for whatever reason) may go unnoticed when you use a web browser, but become immediately visible when you need to maintain a long lasting connection.
That said, from your description I can guess that your Host connects to the server on the same machine. In the Host's internet ID settings try specifying the server name as "localhost" or "127.0.0.1" instead of the server's external IP/DNS, to eliminate a possible loopback issue.
In either case it would help to look at the Host log.