adb server version (41) doesn't match this client (39); killing..

This error message indicates that the version of the Android Debug Bridge (ADB) server running on your computer does not match the version of the ADB client you are using. This can happen if you have multiple versions of the Android SDK installed on your computer or if you have updated one component without updating the other.

To resolve this issue, you can try the following steps:

1. Update the ADB client to match the version of the ADB server running on your computer. You can do this by updating your Android SDK or by downloading the latest version of ADB from the Android Developer website.

2. Restart the ADB server by running the following command in a terminal or command prompt:

adb kill-server
adb start-server

3. If the problem persists, try restarting your computer and then starting the ADB server again.

By ensuring that your ADB client and server are running the same version, you should be able to connect to your Android device and debug your applications without any issues.