React+mobx does data management, why can't the parent component read the changed values in the child component store?

the store, of child component B is injected into parent component A through the inject method. After changing the value of @ observe through the @ action method of component B, it is read in parent component A. the result is that the initial value has not changed. Why?
there is no code because of the problem of tapping with the mobile phone. Please give me some advice from the gods

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Mar.09,2021
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