Let's perform some troubleshooting steps by resetting the password of your Intuit account. Just make sure the Customer Account Management Portal (CAMPs) uses the email address you registered your product with. I'll guide you how.
Once you're logged in, you can now change your QuickBooks Desktop payment method.
Otherwise, a request can be made to change your Intuit account email address here if you no longer have access to it. Then, I suggest reaching out to our QuickBooks Customer Care Support Team. They have the tools to update the payment method on your account and help you further with your change e-mail request.