My model was animation ready then the hair stopped following the model

Question

With my model, I finished rigging it, all of the hair followed the head and it was perfect. Then I added a skirt and rigged it and suddenly the hair is leaving huge chunks of it behind and now I'm absolutely crushed.

Why did the model suddenly play up on me like this? I tested it and everything was fine but now the hair is suddenly refusing to follow the model.

Plus due to copyright(since this model is for a game) I'm not allowed to upload or share it, which makes the situation even more grim.

Can anyone think of what is causing part of the hair to stop following the armature?

When I click on the vertex group for the head bone, it shows the entire head and neck highlighted with the parts of the hair also highlighted that moves but when I try selecting all of the hair and clicking "Assign" the neck becomes stiff and refuses to move like it did before. I'm seriously out of ideas at this point.

Answer 1

I found out her to fix it but I also want to explain the difference so this makes more sense:

Because I had edited the model(shoes, skirt, clothes) it made the model stop following the armature, so when I used Automatic Weights on it, the hair didn't follow the model's head like when I first tried rigging it.

To fix this and get the model's hair to follow it's head, rig it how you normally would(in this case, automatic weights) then select the armature and go into pose mode. Once you do this, select the headbone and then select your model again.

Go into weight paint mode and paint the hair so it's all red, then go back to the armature's pose mode and rotate the head to check if you selected it all.

This is how I got the hair to follow the model's head and because my model has several textured planes, this helped me avoid the nightmare of having to delete them all(and I have everything as one object) to remodel the hair, so I hope this helps you if you're stuck on this issue :)