The error about meshing

When I finish setting the boundary condition and voltage and proceed to the next step, the SPIS prompts that there is an error in meshing.
Such as “Error in UI2NUM ThreeDUnstructVolMesh.autoThinSurfaces:volume mesh surface 1386 has no neighbour cell and duplicates a surface with no neighbours!”
And sometimes when I finish modeling with gmsh and import it into spis, spis does not display the model.
Please help me. Thank you!