Can connect via CloudLink, but cannot connect via myQNAPCloud

[teutsch]

My apps DO connect to my NAS from outside with my phone apps via CloudLink (only). So that's fine. But MyQNAPcloud login or WAN address login with the apps does NOT work.
Furthermore, if I login to myQNAPCloud and click on my device, I get the message "CloudLink not installed or does not function correctly".
Well, CloudLink IS installed and my phone apps work, so what does not function correctly and prohibits me to log into my NAS via myQNAPCloud?
I recently had a new modem connection from my ISP. Could that be the problem? What I noticed is that the WAN IP (public IP) in myQNAPCloud (when clicking on device detail)
is the old WAN ID. The phone apps have the new one already. So perhaps that's the problem? So how can I change the WAN ID in myQNAPCloud? I thought that this would be solved automatically?
Pinging MYDEVICE.myqnapcloud.com pings the old WAN ID as well. Something wrong with DDNS?
Can I somehow "refresh" my devices? Or do I have to re-register my device name?
Anyhow, even if I ping my new WAN ID I do not get a connection (because it's on a subnet?). So how does CLoudLink work then on my phone apps? It's all very confusing.
Any thoughts or an explanation how CloudLinks works while myQNAPCloud does not work?