I received an email from Google that we need to start supporting 64-bit CPUs in our Android apps by August 1, 2019. In their documentation, it states that there should be a lib/
As @sushihangover mentioned, you just have to Make Sure that on your "Release" configuration, you need to select the arm64-v8a ABI configuration. Remember to "Rebuild All" before you hit "Archive for Publishing" so that you don't run into issues based on cached data. You can view this article for more details and a video.