When I click on Update button, domain *.myqnapcloud.com is updated without any problems. Of course, that service has not sense if I have to update it manually

What was changed in my Qnap (TS-251) in the last days? I upgraded RAM from 2 to 8 GB and I installed Container Station and Browser Station. That's all.
Do you have any idea, what should I check, why DDNS doesn't work automatically?
m@k