Your app is sending Advertising ID over an unencrypted connection.
This isn't recommended because network intermediaries might be able to intercept it. You should use an encrypted connection when sending Advertising ID.
In logcat ads request is going through this url http://ads.mopub.com/ and not https://ads.mopub.com/
Am getting this type of warning in google play store console pre launch report when uploaded my apk to alpha testing