If the Cloud installation program issues you a code and tells you that it is already in use when you attempt to connect it to your Cloud account, there is a problem with the computer's root system - essentially, the computer is using the same Identifiers as another computer connected to Cloud (MachineGUID).

For clarity, this means that the computer you are using has probably been cloned or imaged incorrectly, and the identifiers inside the Computer's Registry are identical to another machine already registered to Cloud. Contact your IT department and ask them if the machine is cloned and if a program called SYSPrep was run during the cloning process. 

As a side note, running cloned machines with identical Identifiers is an illegal practice and should be corrected upon discovery.