Seeing “Fail to get the next controller step 2 – 0” in the Download Server Diagnostics Window (or similar message) when attempting to download to controller.
There is a problem with the encryption between the client and controller. It's possible only one end of the connection is encrypted and the controller may have been defaulted. You can tell this by looking in the Event Server Diagnostic Window which will usually show entries similar to "Encrypted Packet Received".
Remove encryption by selecting Disable Controller Encryption and attempt to download the controller.