If you see the following error:
RealVNC Server is not licensed correctly. Connections will be prohibited until a valid subscription is applied.
...then it may be that RealVNC Connect is conflicting with an offline license already present on your system from an earlier, incompatible version of our VNC software (version 4.x or 5.x).
If you know that you've had legacy VNC software from RealVNC installed on the computer before, then you'll need to remove the old offline license. It may be that simply restarting RealVNC Server is sufficient to solve the problem. If not, then follow the platform-specific instructions below.
Note: If you've never had legacy VNC software installed on the computer, then this error means something else is wrong with your VNC Connect subscription. Please contact us.
In an Administrator Command Prompt, run the command:
"C:\Program Files\RealVNC\VNC Server\vnclicense.exe" -remove
If this does not help, check the Registry for values referring to
vncserver_license in the following locations:
If there are no matching values, please also check for
Mac / Linux
In a Terminal window, run the command:
sudo vnclicense -remove