Android Studio - ADB start server fails, adbkey check fails

Solution 1:

It is a bug with the latest version of the platform tools (27.0.0), the solution I found was to downgrade to the previous version.

Remove the current platform-tools directory located in the android-sdk directory, then download the older version from here:

• Mac: platform-tools_r26.0.2-darwin.zip

[Update]: Some users (myself included) have noticed that the issue only happens when your phone is plugged in, so if you don't need to test on it, try to unplug it and use an emulator. Also worths noticing that all reported devices were from the Google Pixel line, so other devices might not cause the issue.

[Update 2]: This seems to be solved in the latest update of the platform-tools (27.0.1).

Solution 2:

To add to the answer, here are some commands to quickly rollback on Macs. This was borrowed and tweaked from a helpful post in the bug tracker

cd $ANDROID_HOME && rm -rf platform-tools/ && curl https://dl.google.com/android/repository/platform-tools_r26.0.2-darwin.zip -o platform-tools_r26.0.2-darwin.zip && unzip platform-tools_r26.0.2-darwin.zip