1. You have to fix the problem in the mesh. The mesh in the connection between the cylinder and flat plate as you can see in the attached figure.
2. Click Control ->Degrees of Freedom, then uncheck X-Rotation, Y-Rotation, Z-Rotation.
3. Forget about Fluid Structure Interaction (FSI) for the moment and just run the time-history analysis of solid mechanics to see if you can get correct answer.
4. Don't use Automatic Time Stepping Scheme right now.
5. Once you feel comfortable about all the relevant inputs. You can add FSI and solve the problem you want.