I opened edited assembly 1 22 midsrfc.x_t and see that it has three different thickness walls. Is this intentional?

When you sliced off a section of honeycomb, you left hanging faces like this.

It's best to delete the leftover face.

After cleaning up all the hanging faces, I have this solid model.

After using the Midsurface feature in NX, I get this set 

I could not Sew (equivalent to SW Knit) these surfaces into one body. That's okay, I will see if DM will connect the surfaces using Shared Topology.

Here is the parts in DM using Share Topology.

Here is the mesh in Mechanical. We can see that Share Topology failed because there are red lines at the Y intersection.

There is a Node Merge feature that can connect things together. The purple is correct for the Y connections.
I am a bit concerned about the black line on the one edge that should be red.

Unhiding the Top and Bottom sheets shows that the Mesh Defeaturing has connected those sheets to the honeycomb where the lines are black not red.

I defined contact elements to connect the top edges of the honeycomb to the top sheet, and the bottom edges to the bottom sheet.

Attached is zip file with the Parasolid and an ANSYS 19.1 archive.