It seems that the domain mynetname.net expired a moment ago.
So, all /ip/cloud DDNS names have vanished.
I sent email Mikrotik support as it happened, and very exceptionally, also called a POTS call to their Riga switchboard. The switchboard is still very reluctant to connect to anybody, but as I repeated that the situation was critical, I asked her to write down the issue, word by word. Then she contacted their support, and after a short while, reported to me that they were (now at least) knowledgeable of the situation, and are working to fix it.
So, as of now (since 6-Sep-2021 10:49 UTC) many tons of businesses are down, tons of VPNs are down, and we are all waiting for the xxxxxx.sn,mynetname.net to start working nicely again.
This really is a major screw up by Mikrotik, I hope they will learn to maintain their production domains and other relevant services much much better.
For emergency resolving of DDNS names, you can ask directly from the mynetname.net NS-resolvers (159.148.147.201 and 2a02:610:7501:1000::201, 159.148.172.251 and 2a02:610:7501:4000::251). Not of course valid recourse in every case, but it does help for some of the emergent cases:
dig @159.148.147.201 dead42babe.sn.mynetname.net