I acquired a paid Addon that works when I get that same error on some of my rigs. Well recommended by me. Do your normal Automatic Weighting, then run this on your setup.
Surface Heat Diffuse Skinning, and Voxel Heat Diffuse Skinning, works every time, for me.
have you tried scaling it up?
Thanks, Sub-serf command worked for me as well. I can vouch for this answer.
i add the same problem and i solved it by scaling/size up the mesh and armature x10 , set viewport shading solid because is lite resource and graphic uses than Material or texture mdoe. so i parented again the mesh with automatic weight and all worked fine.
before doing this i tried to remove double and recalculate normals but the error was persisting.
the mesh i was using had lot of verticles and faces but no separated parts
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thanks!!! buggy blender 
Chances are that it’s not your armature, fix that mesh!!! Here’s how I fixed mine: select your character mesh, tab into edit mode and merge vertices by distance, tweak the slider by the bottom left slightly making sure not to lose details and that should fix the problem.