Add a Modal analysis after the Static Structural so you can drag and drop the Fixed Support.  Then in Modal, it shows you the bodies that are not connected and have a zero frequency.

The problem is that the nodes along the beam on the frame does not line up with the beams on the roof.

The corrective action is to use the Share tool on the Workbench tab in SpaceClaim.

Now the modal has a non zero first natural frequency.

Note: when I did the share, the cables that were to be Links were visible, so they got cut into pieces. Make the cables hidden so they don't get Shared.