Uninstall Guitar Pro 6.
Go to, http://www.guitar-pro.com, click on "My account" and register your license or login if you already have an account.
Click on "Download (full software, RSE banks, manual...)" and on the next page click on the Full GP6 download icon with the OS that matches what your computer is running.
Install this full version of the GP6 program when the download is complete.
Start GP6 and launch the updater from the "Help" drop down menu on a PC and from the "Guitar Pro" drop down menu on a Mac.
You may need to run the updater several times to get all of the available updates.