Before the message pops up, just hit Data Link and you will be able to sign in normally.
If the message pops up before you can tap anything, hit OK and let the Title Screen refresh, then hit Data Link again. Rinse and repeat until success.
Once sign in is complete, you should see your player ID on the top right.
Patch MOD.apk over the LINKING.apk and start the 2gb install if needed. If you start the 2gb install using LINKING.apk, then obviously the game will keep detecting it is a third party app and stop your app.