Thanks for sharing some basic troubleshooting steps @Fiat Lux.
Allow me to add more details that will help you in renewing your QuickBooks Online (QBO) subscription, @HenryAmalaraj.
The error code 81594 usually appears when you'll be re-subscribing to QBO and the system detects that the address is incorrect. You can update your business information in the Account and Setting page to fix the issue. This way, you can start managing your business and monitor its progress.
If you're still getting the error message, there may be an issue with your regular browser. Try logging in to your account in private window and make sure that the business address is correct, then resubscribe again. Simply press the following keyboard shortcut keys to access incognito:
You can easily update your credit card info, upgrade your subscription, or make other changes to your account through the Billing & Subscription tab. To learn more about it, kindly refer to this article: Update your billing and subscription information.
Let me know if you have other questions and how this works. I'm just here to help. Take care!