Since the introduction of a new API at Mollie, a few new payment methods have been added. This means you need to check how the payment methods have been configured in RO Payments.
The payment methods selected in RO Payments must be activated in your Mollie account. An overview of the available payment methods can be found in the Mollie Payment Options article.
Let's say in the Mollie account only iDEAL and Bancontact have been activated. In this case you should only select iDEAL and/or Bancontact in your RO Payments profile. If any other payment option has been selected and a customer chooses this payment option that is not active the following error will occur:
Error executing API call (request): The payment method is invalid.
This means that the chosen payment option has not been activated in Mollie. To solve this either remove the payment option from the profile or activate it in your Mollie account.