Unable to assign automatic weights

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some information on what ive done. the model is not mine, and it was imported as an OBJ. ive tried to remove all data from it beside the mesh.
Adding a new mesh to the scene and binding it to the rig works just fine.
Manually adding weight paint to the deformation rig works fine, but automatic weight does not work.

dont be picky on the rig, i know its not set up perfect, but i have enough experience with that rig to know that it should not be the issue.

ive applied all data, rot.loc.scale.

NB! Enable the rigify addon!
please download the file and try to apply automatic weight and see if it works for you.
if it does not, try to see if you can find the issue, and report back to me even if you could not resolve it. id like to hear if anyone else also had the same issue.

Attachments

rigging.blend (3.44 MB)

The internal faces mess up the calculations. in Edit mode hover your mouse over a body face and press L, and then again over the shoulder piece that isn’t connected. Then Ctrl-I to select the inverse. G to grab, and move those out where you can see them. Delete that junk. And have fun!