why this happened?
go to router page, check the logs tab. It will tell you the sync issue. For example, one of the most common issues is “pppoe server interface does not exist”. This issue happens when you have an interface, you add a pppoe server to it using zima, then you remove this interface in your mikrotik.
It is not a critical one since it does’t affect the graphs reading, however it is better to fix it.
So to fix it, you simply go to router page, interfaces and remove the interface that doesn’t exist anymore. The message stops to appear again.