"Could not associate block entities to geometry" Ansys Meshing - How do I fix this?
 

Hello, I am trying to associate my mesh block structures to my geometry on ANSYS Spaceclaim.
Could anyone explain to me why the error "could not associate block entities to geometry" occurs? Sometimes I can run an airfoil, like the one in this case, just fine with no issues. Other times I can not find a solution online or a work-around for this error - and I usually have to restart.

What does this error mean, why does it occur, how do I fix this?

My domain is a simple 2D airfoil simulation, 1 element thick in the "3D direction". I have splits going down the front middle and back, as well as the top and bottom, and sides (though this region has been deleted because I can use symmetry BCs.

Thank you and feel free to ask any questions.