Apple have added a new security layer to macOS 10.14 Mojave. After upgrading your Mac to Mojave, VNC Server will allow only view-only remote access until such time as you've granted access to the
vncagent application (installed as part of VNC Server). You see the following dialog:
You cannot grant access remotely; you must grant access locally before establishing a remote session.
To do this, open System Preferences > Security & Privacy > Privacy > Accessibility. Click the lock button to make changes, and + to add a new app to the list allowed to control your computer. Navigate to
/Library/vnc/vncagent and select the Open button:
You should now be able to establish a remote session and fully control your Mac. Please let us know if this is not the case.