I’ve never seen such a message, and I certainly have never had to restart the server for a license import to take effect. Quite curious.
Assuming you’ve received the license file via email: how did you transfer the license to the server? I highly recommend you do not try to do anything via copy & paste. Instead save the license file in your mail client to a text file, then transfer the license file via scp (on a Windows client you can use WinSCP) to the server, log in, run