I am unable to update payment method for subscription.

Make sure to update your payment information through a web browser, @kgharsch. 

Ensure to use the accepted payment methods for QuickBooks Online. A debit or credit card (MasterCard, Visa, Discover Card, or American Express). 

Here's how to edit your card info:

1. Go to the Gear icon and choose Account and Settings.
2. Choose the Billing & Subscription tab, then click Edit payment method.
3. Add the preferred payment method by clicking the drop-down arrow, then fill in the necessary fields.
4. Submit the changes.

See this update the payment information for your subscription article for more information. 

I'm always here if you need help or assistance in updating your payment method. Just leave a comment below.