Kinematic simulation problem

I'm now trying to simulate a v6 engine. I have a problem when making a simulation. After it said the mechanism can be simulated I make a simulation and it works well but when I save the file and re open again the mechanism cannot simulate although DOF is still 0. How can I fixed this problem?

2 Answers

If you share your file, maybe we can find solution.

Check Is there Any part is missing in assembly or may link have break between the parts.