Firebase App Tracking

Hi everyone, I have a doubt about app tracking on my application. I don't advertise the user of my application but I use Firebase token to send the user some push notifications. I don't understand if I have to show the ATT's popup at the first start or if it is not necessary. If I have to show the user the popup and it is declined, will I have to stop using firebase token?

Firebase App Tracking
 
 
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