The reason for this error message is that support for Plaid has been recently deprecated, and so it will no longer work for payments. Now, what you can do to accept bank transfers and ACH payments is switch to Stripe Elements.
To switch to Stripe Elements, go to the Payments page, and select Elements, as shown below.
You can add fee labels or surcharges here. Be sure to click "Save" further down on the page when you're done.
Once Stripe Elements has been enabled, all of the available payment methods from your Stripe Dashboard will appear with options to enable/disable.
To learn more about setting up Stripe Elements, take a look at the full article!
Note: Please be aware that Stripe Elements does not currently support Subscriptions, and we are in the process of completing this update to ensure full compatibility.