Acquia Cloud API v1 will be deprecated at a date in the near future (Apr 15, 2020 at the time of this publication). Since Acquia Dev Desktop uses the Acquia Cloud API, it's important that all users of Acquia Dev Desktop ensure that they have upgraded to use Cloud API v2 prior to this date.
The latest version of Acquia Dev Desktop supports both Cloud API v1 and v2. Existing Dev Desktop users must manually upgrade to Cloud API v2 by following the process described below. New users will use Cloud API v2 by default.

How to check if you are using Cloud API v1
- Open the "preferences" (Mac) or "settings" (Windows) pane.
- Click the "Cloud" tab. If the Cloud tab does not exist, you must update to the latest version of Dev Desktop before continuing.
- If the current API version shows as "version 1", you must upgrade. If this tab indicates that you are not logged in, follow the instructions below to refresh Acquia Cloud sites.
How to switch to Cloud API v2
- After following the above steps, click "Reconnect to Cloud with API v2" on the Cloud settings tab.
- Generate an API token pair from your Cloud account settings.
- Enter your API key and secret in the Dev Desktop login window and click login.
Troubleshooting
If you have any problems using Cloud API version 2, you can roll back to version 1 prior to the EOL date by changing the setting in the Cloud settings pane.
If you are not logged in or connected to Cloud, you can click the "more" button and then "Refresh Acquia Cloud sites" in order to connect.