As stated in the error message, you should check either if:
* the address of the remote server and the repository name are formulated correctly,
* the SSH key used to establish the connection is properly configured to be recognised on the remote repository. It may have been the case for the development environment, but since you UAT environment should be operating from another machine, then you should also configure a separate SSH key for it.
Given the nature of this issue, I'd suggest you get in touch with your systems administrator who will be able to help you on it.
Hope this helps!