Difficulty Rigging a character - "Failed to find a solution for one or more bones"

I have a mesh (https://drive.google.com/file/d/1kIhulNpz5lPmC9PnmEtuWLcC3ov7yIPN/view?usp=sharing) that I’ve been wanting to rig with an armature. But when I go to parent the mesh with Automatic Weights, it apparently can’t seem to “find a solution for one or more bones”. It doesn’t do any automatic weight painting, so I have to do it manually - each and every finger segment included. And even then, it behaves weirdly, moving bits of other parts of the mesh that I hadn’t even painted yet…
Why can’t the Automatic Weight system function? Any advice on how to fix it?

Without looking at your file, the usual reasons for this are:

  1. Non-manifold vertices. (Bits hanging in space on the inside of the model, etc. there is a command to find them…)
  2. Un-connected vertices.
  3. Duplicate vertices.
  4. Bad normals. (some faces inside out - CTRL+N to fix)

Check the topology for your mesh, you will find errors that stop the automatic weight assignment and FUBAR things when you try to do it yourself. If Automatic Weights doesn’t work, don’t try to do it yourself manually, that will not fix the root cause of the issue…

Cheers, Clock.