I suggest you use No Separation for contact between the vertex and the horizontal surface. That seems reasonable. 

Static Structural models don't like to start when there is zero stiffness in any of the 6 directions (3 translations, 3 rotations) of one body relative to another (or ground).  For example, if the diameter of the beam is 50 mm and the internal dimension of the square tube is 52 mm, then there is 1 mm of clearance on each side of the beam if it is positioned in the center of the tube. That means the beam has zero stiffness in 5 directions (since the vertex on the bottom face takes care of Uy).

The corrective action is to tilt the beam so the beam is in the -X, -Z corner of the tube at the bottom and at the +X, +Z corner of the tube at the top of the tube, and the Wind Load must be in a direction that includes positive forces in the +X and +Z direction so that it continues to push the beam into those two corners.  Now the beam has stiffness in 6 directions. Rotation about Y is taken care of by the Coefficient of Friction.

If that seems like a lot of work, you can simply make the beam have the same dimension as the ID of the tube. But, you must insert a Contact Tool under the Connections folder and Generate Initial Contact Status. The contact must be Closed.  If it is Near Open, it might have a tiny gap. That is still zero stiffness. Increase the beam diameter by a tiny amount until the contact becomes closed. The benefit of this approach is that the wind load can be in any direction.  With a tilted beam, if the wind load was to push the beam away from the corners it was nested in, that might cause the solution to fail.