Never use default credentials for your VNC Server.
To ensure uninterrupted access to VNC Server features and updates, it's essential to keep your license key and serial number up-to-date. Here's how: vnc server license key serial number upd
If you are running VNC Server 5.x or 6.x (pre-VNC Connect), you can locate your existing serial number in three places: Never use default credentials for your VNC Server