We had installed SharePoint 2016 Server Enterprise (Trial) as a farm. Wherein we have 1 App Server and 1 Web server. Both are VMs on same host machine. For making the installation licensed, had gone to Central Admin > Upgrade > and entered the License key on Web server. It worked as expected. However after this when tried to same on App server, found that the license textbox is disabled. We don't know why it is so? Is is that for a farm entering license key on 1 server is enough? Or we have to enter key on both servers? If yes how we can do it?
Have attached snap shot for reference.