When a customer tries to add a New Payment Method through their Online Account in SedonaWeb and receives this Error Message

This is most likely due to the Setup of the Payment Methods in Sedona Office.
Sedona Office
Go to Sedona Setup and select “Payment Methods” under CM.

Make sure All Payment Methods are marked “N” for Inactive.

If a Payment Method is showing “Y” under Inactive and should be Active, then select that Payment Method and unselect the “Inactive” checkbox. Apply.

If All Payment Methods are Active then make sure the Payment Method Field is spelled out and not abbreviated.

If a Payment Method is misspelled or abbreviated, update the Payment Method field, and Apply.

Now the customer should be able to add a Payment Method through their online account in SedonaWeb.