You didn’t use Form New Part correctly in DesignModeler so you have a lot of contacts and the mesh doesn’t line up.

Right click on Diaphragm and Explode the Part, then select all the bodies and Form New Part.

Now there is no contacts and the mesh is connected.  I also reduced the element size to 25 mm.

If you take the surface of the Diaphragm and extend it out beyond the Layer1 solid, then Slice Layers 1 – 3, you will get hex elements on Layer 3 instead of Tet elements.

I also found that in Mechanical, the Layer 1, 2 and 3 solids were assigned to Structural Steel and not Bamboo L1, 2, or 3. Make sure to check material assignments!