Sometimes mesh generation fails if seeds are overconstrained. Several options are available to handle the overconstraints.
When Abaqus/CAE is unable to create a mesh because of overconstrained seeds, the following dialog box appears: In addition, the overconstrained seeds are highlighted in the viewport. You can choose one of the following options:
Click Yes to relax the seed constraints and to continue meshing the region.
Click No to save the seed constraints and to cancel the meshing procedure.