I can add a bit more information on how to resolve the "Something's not quite right. v4error.SUBSCRIPTION-81511" error when trying to update your billing information inside QuickBooks Online.
This error message is a generic alert that is caused by issues like:
Invalid Address. PO Boxes cannot be used as billing addresses.
Invalid Credit Card
Payroll is still active when trying to resubscribe.
To rectify this, try to enter your Billing Address Details without special characters such as hyphens, commas and periods. You can also contact the Credit card provider for them to allow payment processing. Trying another Credit Card can also help.
However, if none of these workaround fixes the issue, I would recommend contacting our Phone Support Team. They have the tools to update your account billing details in a secure environment, which I'm not able to do in this public forum.
Perform these steps to get our contact information:
Click the (?) Help menu at the top right section of your QBO Dashboard.
Tap the Contact us button.
Please let me know how the troubleshooting steps goes. I'll be here to help whenever you have any questions or need further assistance. Have a nice day!