hey i have a problem with converting from Polygon to subds
it says that it failed to convert

so i opened the script editor to check the problem
and here what it says

// Error: polyToSubdiv1 (Poly To Subdiv Node): One or more edges is nonmanifold.
// Nonmanifold geometry cannot be converted to a subdivision surface.
// To clean up nonmanifold edges, use Polygons->Cleanup with the nonmanifold option. //
// Error: Command polyToSubdiv failed. Open Script Editor for details. //

what should i do