Change the "android:name="com.google.android.gms.wearable.MESSAGE_RECEIVED" action from your manifest to "android:name="com.google.android.gms.wearable.DATA_CHANGED"...

I don't know whether in fluter is the same, but usually you have to set a data tag to the intent, e.g.:

<data android:scheme="wear" android:host="*"

android:path="/start-activity"

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