In past few releases there is “auto” and “on” for DDNS settings. The “auto” means off/disabled — unless you enable “BackToHome” features.
The IP Cloud docs, https://help.mikrotik.com/docs/spaces/ROS/pages/97779929/Cloud#Cloud-DDNS say:
Before 7.17, the default value for ddns-enabled was “no”. In versions after 7.17 and including, if you want to disable DDNS, make sure to disable the Back To Home feature first, if it was enabled, then set “ddns-enabled=auto”
I don’t think they updated the securing your router page to reflect =auto.