React Native app doesn’t lock the screen when app is left open

I have React Native app and it doesn’t lock the screen when app is inactive. The application doesn’t lock the screen after inactivity.

Tell me please the reasons for this problem and how it can be solved. This is my activity in AndroidManifest.xml:

      <activity
        android:name=".MainActivity"
        android:label="@string/app_name"
        android:exported="true"
        android:configChanges="keyboard|keyboardHidden|orientation|screenLayout|screenSize|smallestScreenSize|uiMode"
        android:launchMode="singleTask"
        android:screenOrientation="portrait">