Which segment are you using? Please note that if you are using All players and your player number base is extreme large, it won't work. May I have your title ID?
My title ID 1B2EA, I'm currently using "Scheduled Tasks".
I have checked your title. Besides of "InvalidParams" errors for some other APIs, which is normally caused by improper API requests, the error returned from SendPushNotification Server API call is PushNotEnabledForAccount.
Besides of configuring Push service on Game Manager, you may also need to register the device for the player to enable push service. Would you double-check the player account? Please refer to Push Notifications Tutorials - PlayFab | Microsoft Docs
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