After converting a mesh to polyhedrals, layering no longer works, even if the layering zone is hexahedral.
Once you convert a mesh to a polyhedral mesh in Fluent software, that mesh cannot be layered. It may seem like a hex mesh is unchanged after conversion, but its representation is altered to a form that's not compatible with layering. If you want to convert the tet zones to polyhedral but leave the hex/prism zones unaffected, do the following:
1. Generate the layering zones in a separate mesh.
2. First, import the tet zones into Fluent software and convert to polyhedrals.
3. Use Setting Up Domain > Append Mesh to append the layering zone mesh to the polyhedral mesh.
After doing this, you should find that layering will work.