I am having the exact same error. Win 7 x64 connecting to server 2012, just downloaded NoMachine.
Yes I read https://www.nomachine.com/AR02L00784 and clicking the icon does nothing.
Can’t send a cntl+alt+del = can’t login.
Everybody else seems to use a macro for it cntl+del, cntl+alt+ins, cntl+alt+end… Have you thought of that?
Or how do I get the icon to do something?