Download the file linked to above, open the Model in Mechanical, click Generate Mesh and you will get the same mesh I get unless you change something first.

If you opened the Geometry in DM, then did a Refresh and opened the Model, you may have lost the 4 Faces that were made with Virtual Topology.  Recreate the Virtual Topology and it should mesh again.

I created a ZX plane in DM to cut the length of the bamboo down to a small length so I could mesh and solve the model with the 3 mm element size that gives 2 elements through the thickness of each layer and solve in the Student Limit.

I can change the Element Size to 6 mm and get 1 quadratic element through each layer wall thickness.