Achievement Notifications after upgrading to Unity 5.3.1

I'm in the process of upgrading my iOS build from 5.1.3 to 5.3.1, and I noticed that after the upgrade, achievement notifications do not appear in-game when the achievements are satisfied. Is anyone else experiencing this problem?

Also, I'm using iOS Native Plugin from Stan's Assets. I'm not sure if it's a problem with this asset either, so I'll be cross-posting in the specific support forum just in case.