Android Studio (Preview) sometimes recommends updating to a Gradle Plugin that is not available yet (did Google forget to publish it?). Such as today with
'com.android.tools.build:gradle:3.1.0-beta1'
I found I can see current versions of com.android.tools.build:gradle here, and then I just pick the newest:
https://dl.google.com/dl/android/maven2/index.html
I just found this beta1 gradle bug in the Android Bug Tracker. I also just learned Android Studio > Help Menu > Submit Feedback brought me to the bug tracker.
Found temporary solution at androiddev reddit for the 3.1.0-beta1 problem: Either roll back to Preview Canary 8, or switch to gradle plugin 3.0.1 until Canary 10 is released shortly.