If I recall correctly, PrintMusic can only be authorized on one machine at a time. If it is authorized on your iMac, you would have to de-authorize it there before trying to authorize it on your MacBook.

Ordinarily I would advise you to call MakeMusic if you are having an authorization problem, but that may be much more difficult from Korea than from the U.S.

This is the error you get if the serial number is already authorized on another computer or is wrong. A bad internet connection cal also cause it. Sometimes, people are running port blockers such as Lil Snich — the license needs to be able to connect to the Authorization Server.

It can happen that your router or isp is blocking the port that the license manager needs to use.