Hi Chris
I forced an update to see what response was from dynamic.zoneedir.com, and here's the DDCLIENT log file
INFO: forcing updating 30ct.carnegie-dixon.com because no cached entry exists.
INFO: forcing updating carnegie-dixon.com because no cached entry exists.
INFO: forcing updating mail.carnegie-dixon.com because no cached entry exists.
INFO: forcing updating no30.carnegie-dixon.com because no cached entry exists.
INFO: forcing updating
www.carnegie-dixon.com because no cached entry exists.
INFO: setting IP address to 86.190.210.5 for 30ct.carnegie-dixon.com,carnegie-dixon.com,mail.carnegie-dixon.com,no30.carnegie-dixon.com,
www.carnegie-dixon.com
UPDATE: updating 30ct.carnegie-dixon.com,carnegie-dixon.com,mail.carnegie-dixon.com,no30.carnegie-dixon.com,
www.carnegie-dixon.com
CONNECT: dynamic.zoneedit.com
CONNECTED: using HTTP
SENDING: GET /auth/dynamic.html?host=30ct.carnegie-dixon.com,carnegie-dixon.com,mail.carnegie-dixon.com,no30.carnegie-dixon.com,www.carnegie-dixon.com&dnsto=86.190.210.5 HTTP/1.0
SENDING: Host: dynamic.zoneedit.com
SENDING: Authorization: Basic UENhcm5lZ2llOmV1aDY2d3owbjNkMXQ=
SENDING: User-Agent: ddclient/3.8.3
SENDING: Connection: close
SENDING:
RECEIVE: HTTP/1.1 200 OK
RECEIVE: Date: Thu, 30 Sep 2021 19:19:31 GMT
RECEIVE: Server: Apache
RECEIVE: Vary: Accept-Encoding
RECEIVE: Content-Length: 196
RECEIVE: Connection: close
RECEIVE: Content-Type: text/html; charset=UTF-8
RECEIVE:
RECEIVE: <ERROR CODE="702" PARAM="600" TEXT="Minimum 600 seconds between requests" ZONE="30ct.carnegie-dixon.com,carnegie-dixon.com,mail.carnegie-dixon.com,no30.carnegie-dixon.com,
www.carnegie-dixon.com">
FAILED: updating 30ct.carnegie-dixon.com: 702: Minimum 600 seconds between requests
FAILED: updating carnegie-dixon.com,mail.carnegie-dixon.com,no30.carnegie-dixon.com,
www.carnegie-dixon.com: no response from dynamic.zoneedit.com
It does look like dynamic.zoneedit.com is online, but the response being handed back is not thye same as previously sent back to ddclient.conf, or that which the BT Home Hub 5 has been expecting all these years.
Hope this might help diagnose the issue more quickly
Peter