Briefly, I cannot connect to Pi-hole when I use the configured IP address of the Raspi machine. But I can ping it and use the web interface.
I first discovered this on a Windows client, but the problem seems to be more fundamental, as shown by this telnet session on the Raspi. I can connect to Pi-hole using the loopback address, but not the address on the local network:
There is also a problem with the dashboard, as illustrated below - the data never appears. I haven't really started trying to solve this myself yet, but I mention it here in case it is relevant to the main issue. It also demonstrates that the IP address on the local network is in itself OK, and Pi-hole is installed there.
Any help much appreciated!