PSA: Do not use platform-tools 28.0.2 with the emulator. Play store AVDs will not work with adb (unauthorized). Use platform-tools 28.0.1 instead.
If you've installed platform-tools 28.0.2, the emulator is broken for play store AVDs (adb unauthorized):
https://issuetracker.google.com/issues/128894733
Replace contents of Android SDK folder with the following, depending on your OS:
https://dl.google.com/android/repository/platform-tools_r28.0.1-linux.zip https://dl.google.com/android/repository/platform-tools_r28.0.1-windows.zip https://dl.google.com/android/repository/platform-tools_r28.0.1-darwin.zip
Then:
rm -rf ~/.android/adbkey*
adb kill-server
adb devices
Wipe data of play store AVD.
(We're working on a fix.)