Application Studio has a command-line script for repairing its connection to the database. You need this tool if the database has been moved to another server or the credentials for connecting to the database have changed.
The script is repair.sh and is in the <install directory>\cli-tools directory
Invoke the script by executing repair.sh datasource.
The script prompts you to select a database type. Then you can change or keep the current connection settings as needed.
Restart Application Studio after running the script. In the administration user interface, your changes override the datasource settings for the currently selected profile at System Settings > Datasource & Profile Settings.