If you are being prompted to purchase the software again, you need to make sure that your software is properly activated.
The instructions for resolving this issue differ depending on the version of the software you have:
Account-based version
Please open the software and sign in to your account using the email you used during the purchase and your account password.
Key-based version
You can find your license key/serial number in the purchase confirmation email. Copy and paste it to activate the software when prompted.