Hi Winho,
It looks like the issue is happening because the file is still linked to the original serial number, which is why you're getting the authorisation error. To fix this, you'll need to contact our live chat support through our virtual assistant MOCA or submit a case via MyAccount. They'll be able to process it for you and guide you on the next steps.
Just a heads up, removing the serial number will affect your original file. If you're testing with a dummy account, it's best to create a brand-new file instead of using a backup from your main business.
Regards,
Sai