Figured out how to fix this — just manually install the firmware (even if there’s no newer version; it can be the one currently installed on the router), and the cloud now works as before.

@Joseph-TP thanks for reply, but the problem is not so common :) router can't connect to some tplink web services - tplink cloud (settings, register or restore password - you can see that on my...

Suddenly DDNS stopped working, the domain name is resolving but settings are not available