I am trying several time to figure out how to fix a bug where my model doesnt bind to the bones

I tried to had 2,3 wwskin binding in a one model but then ,the only had been reading is the first binding ...

Note:The only bone that doesnt cooperate is vertices in knees ,i dont know why and that was Sheting me.

Pls i need help about this .... or a tip to bind models and bone properly

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