Shelly EM stop send data to cloud.

Sometimes I have the same issue, I think that it's related to the WiFi connection, at least in my case. I have a main access point and a WiFi extender. When the Shelly EM connects to the main access point the WiFi signal is weak and I see that for many hours there is no data in the cloud. If I reboot the Shelly it connects to the extender which is closer and so the WiFi signal is stronger. In this case it works fine and the data in the cloud is up-to-date.

You may try to verify the WiFi signal strength in "Settings -> Device Information". If it's weak this could be the reason.