D5 does not sync with Sketchup

Hello! I have a problem with the synchronization of my sketchup 3D model for D5. The update model button doesn’t activate and I can’t re-sync it. What is the problem and the solution?

Thanks!

The model cannot be updated in synchronization status. The key point is to update the model button.

Before that “update” button was activated in D5 but not now. And I don’t understand the reason