'No available sessions' is issued when connecting to the Mac login screen
When the remote Mac is on the login screen, users connecting by NoMachine can receive message <No available sessions on this server>.
As a possible workaround, try to restart the nxserver on the Mac via SSH by executing in a SSH terminal:
sudo /etc/NX/nxserver --restart
If the problem persists, you may try to enable the automatic login on the Mac from the Apple menu > System Preferences.
SOLVED, Released in version 7.0.208
