Please follow the steps below to address the issue.
Method #1
1). Close the AVANT program.
2). Right-click on the AVANT icon and choose ‘Properties’
3). Click on the ‘Compatibility’ tab
4). Place a checkmark next to ‘Run this program in compatibility mode for’ section and choose ‘Windows XP Service Pack 3’
5). Place a checkmark next to ‘Run this program as an administrator’ (you do not need to be an administrator to do this).
6). Click the ‘Apply‘ button then the ‘OK‘ button.
7). Run the AVANT software (if you see a Windows message about the program making changes to your computer, click yes).
8). Try to register again. You will now be able to register going forward.
Method #2
Using Windows Explorer, browse the Avant disc and open the Support folder.
Inside the Support folder, select Regmate and then right-click on it and choose Run
as administrator from the context menu.
The registration assistant will start.
Click the Install button and allow it to complete. It runs very quickly and once
completed, just close it and then return to your Avant software to re-try the
registration.