This error is given with the driver does not see a supported tablet connected to the computer. First, please make sure the USB cable for the tablet is connected directly to the computer and the tablet is powered on. Avoid using USB hubs, keyboard/monitor ports, or docking station as these can cause intermittent issues.
*If on windows, please make sure when connecting the tablet, the Windows device driver installs and says the installation is complete before using the tablet. If it does not install or gives an error, try running your Windows updates with the tablet disconnected and restart the computer, then try connecting the tablet again.
Once connected if you continue to receive the supported tablet error message, the driver currently installed may be the incorrect driver for the tablet. For example, the Intuos 3 tablets are no longer supported on the current Wacom driver, the last supported driver for that tablet is the 6.3.15 driver. Please make sure you are using the correct driver for your tablet found on the Wacom Driver page.
If the issue continues, or if you receive no power light on the tablet when connected, please contact Wacom Support.