Anytime you receive a PRODUCTS_NOT_SUPPORTED error, refer to the error reference in our docs for common causes and troubleshooting steps.
For Capital One accounts, an additional common cause is that the Identity product is not currently supported for Capital One credit card accounts. Requesting Identity information (calling /identity/get) when the user is only sharing credit card accounts will return a PRODUCTS_NOT_SUPPORTED error. To avoid this, check the account type (e.g., credit vs. depository) before calling /identity/get, and do not make a request to Identity endpoints for Items that contain only Capital One credit card accounts.