There is a new plugin in the Testing repo for DDNS Services, openmediavault-ddclient. Currently there are only configurations for 2 services, DynDNS and No-IP free. More features/services can be added. We just see if there are any requests.
A Successful update will show in the syslog. If there is no change on the update it will not show in syslog. But you can delete the cache which will force and update regardless if the service needs it. This will leave an entry in the syslog. If you start the service and your current config is not working there is a button to test your config. This will give verbose output and help you to resolve your issues.
At my office I used to only run a DDNS Service on my router. At times the service would become unresponsive. Now I have an ARM device on the LAN that runs a DDNS Service as well. From years of using a DDNS Service on router I find it best to have the router plugged into a battery backup device with AVR (automatic voltage regulation) and Surge protection. This eliminated probably 95 percent of my router issues (lockups, glitches, etc..).