Thanks for posting in our Q&A forum. Form the error message itself, it indicated the problem was related to the target computer.
1.Have you ever managed to remote from mac to the lab?
2.Please follow the steps below to enable remote access in the target computer
Remote Desktop - Allow access to your PC
Remote Desktop - Allow access to your PC from outside your PC's network
3.Try the latest version of remote desktop client for mac or the beta version.
Hope this helps and please help to accept as Answer if the response is useful.