If you could upload the model to this question, we could provide a more specific answer. In the screenshots you provided, I do not see any inertia blocks. The most common problem that causes that error to be thrown are nodes with no inertia associated with them.
In Transmission_model/Transmission Subsystem/Clutches and gears, try adding inertias to the lines connected to each Connection port. That maybe enough, or will at least allow the diagnostic to be more specific.