Skin Envelope not detecting some bones

[Anonymous]

I have a model made of multiple objects, UV unwrapped, and is now being rigged with the skin modifier. At the neck section, there are 3 bones which I would like to affect it at various weights; Spine3, neck, and a little of head. However, the neck just refuses to acknowledge the bone's envelope. I was expecting the weight colors to appear, but it ignored it completely, even though the relevant bones are already in the skin modifier (and even selected, as the picture shows).

I'd like to know how to make the neck (object name BodyNeckPad) to be affected by the aforementioned 3 bones, and why it isn't acknowledging the neck envelope.
Currently on windows 8, 3ds Max 2019, student edition

(since I somehow can't post the file, here's a GDrive link for the file:)
https://drive.google.com/open?id=1-wl2YybwvjvsKTPRgvMwvYUy83ehOhsZ

[Anonymous]

So err... kinda false alarm; Its entire weight was being occupied by another bone. I suppose the question becomes how to smooth weight between 2 bones if total weight must be 1.

[Anonymous]

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@Anonymous wrote:

So err... kinda false alarm; Its entire weight was being occupied by another bone. I suppose the question becomes how to smooth weight between 2 bones if total weight must be 1.

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I wouldn`t waste to much time using the envelopes. An initial pass can be done using the weight solvers(Heat-,Voxel solver).Then use the Skin WeightTools dialog where you can precisely assign and blend vertex weights.