I've been using the method described here:

https://www.dynu.com/DynamicDNS/IPUpdateClient/RaspberryPi-Dynamic-DNS

For several years. Suddenly it has stopped working, but I have no idea why. Has something changed?

Here is the code that has been working:

echo url="https://api.dynu.com/nic/update?username=mine&password=mine&myip=$ip" | curl -s -k -o $dynfile -K

Sorry, I didn't post enough information.

When I run the script containing the update URL the return is "nochg"

But if I do a name lookup on my domain, the IP address returned is the old one, not the new one. Do, it appears that the DNS is not being updated wit the new IP even though the URL returns nochg