If you use the Unity SDK and have not built a new version of your game in a while, you may encounter an error during the Gradle Build process which states that a 403 status code or 502 status code was returned by the server.
The Unity SDK makes use of the Android SDK in order to implement notifications. The Android SDK used to be hosted in a repository on Bintray. Unfortunately, Bintray sunset their hosting services at the beginning of May 2021. This means that the Android SDK can no longer be accessed from Bintray. Older versions of the Unity SDK still try to access this repository, which is why you may be seeing this error.
Note: The current release and older versions of your game will not be affected by this issue as they have already been built.
Solution
If you wish to use the notification functionality provided by DeltaDNA, you will need to update the SDK to v5.0.7 at least, as the older versions of the SDK are no longer supported for notifications.
The Android dependencies for the latest versions of the SDK are now fetched using Unity's gradle build. In order to ensure that the dependencies are correctly fetched, please follow the instructions found under "Android Dependencies" on the Unity SDK Github page.
If you do not require to use notifications and are using a version of the SDK older than v5.0.7, you can strip the notification functionality from the SDK which should avoid the error.