If you receive a message indicating that your license number is not valid, it is possible that it was not entered correctly. Please compare the license number that you entered with the one that you received from AVG. We recommend that you use the copy&paste method to make sure that you enter the license number correctly.
Also please check whether:
Note: If you have lost your license number, please contact us via our License retrieval form to get your full license number.
Why is the license number shown in your AVG incomplete?
After you enter the license or sales number into AVG during installation or activation and it is accepted, your AVG is correctly licensed. The number you used for activation is however never shown in its complete form anywhere in AVG - the last group of four characters is hidden. This is for security reasons, to prevent an unauthorized person to use your license by writing it down from your AVG program.
If you need to reinstall AVG, or you are installing your multiple license on more computers, it is needed to always enter the full license number that was provided to you upon purchase or registration. The short license number taken directly from AVG will not be accepted.
The short license number is on the other hand sufficient for your authentication when contacting AVG Customer Services, and for any common tasks related to your product.