Since SALOME 9.7, there is a bug to create manually a group of face in a mesh is the MESH module.
To reproduce the problem, just create a cube, mesh it with GMSH. Then do a right clic to create a group on the mesh:
- Element type: Face
- Group type: Standalone group
- Content: Enable manual edition
Now it is no more possible to select face in the Viewer.
I checked with SALOME 9.6 and It worked well.