Our Capital One integration (ins_128026) does not provide real-time transaction updates. Therefore, the /transactions/refresh endpoint is not supported for Capital One and will result in a PRODUCTS_NOT_SUPPORTED error. You can use either /transactions/sync or /transactions/get as an alternative to fetch transactions for Capital One accounts.
Please note that Capital One is currently the only integration that does not support /transactions/refresh, so you should not encounter this issue with other financial institutions.