The reason is that the Physical Conserving ports are not connected to any other physical blocks.
The resolve the issue, you need to connect this port to other physical blocks.
In other words, you cannot place blocks like the ones named "Connection Port" and ""Connection Port1" at the top level of a model. They can be used inside subsystems and the output port of the subsystem must be connected so something.
Look at the Simscape demo models for examples.
