ICETCP.PRO and ICETCP.PLUS are compatible with Windows 11!
The license goes on the ice license server (this can be any windows machine with a writable share).The users run configwizard on the server to get a sequence number (normally this is done automatically when the user installs the client portion by running the setup.exe from the server's TCP5_USER share).
2 of 2 users installed means that the license server has TWO not FIVE licenses in it. If they have a 5 user version there should be a separate 5 user license which can be stacked with the 2 single user licenses in the license server then they will be able to install more clients.