Question: I'm puzzling about how to convert differential equations to its transfer function

question.mwWhen I sloving an exercise in my textbook using maple,I had a difficult.

First,I write the differential equation, deq:=[...];then using command,sys1:=DiffEquation(...);I want to get the system transfer function,so I use command tf:=TransferFunction(sys1),but it returns an error[Error, (in DynamicSystems:-TransferFunction) cannot handle input with frequency variable, s].

Then,since TransferFunction cannot worked,I found another way.Fist,using command ss1:=StateSpace(sys1) to get its state equations,but maple ruturns a warning[Warning, incorrect number of state variables specified (expecting 4, received 1), using default values].I leave the warning alone,and typing command tf1:=TransferFunction(ss1),to my surprise,maple returns the transfer function correctly!

Can you tell me why? And how can I slove the fist error and the second warning?

The file has been uploaded.

Thank you very much!