Apparently, a large number of QuickBooks Desktop customers who use QuickBooks Merchant Services have reported that they cannot process payment card transactions.
Intuit recommends that QuickBooks Desktop merchants experiencing this problem manually process any required credit card transactions by going directly to merchant services (http://merchantcenter.intuit.com/) and logging into their merchant service account.
Intuit technical support is currently investigating the cause of the problem.
Insightful Accountant will strive to inform you regarding this incident as soon as information becomes available.
UPDATE: Intuit reports that their engineers have identified the cause(s) of the incident and are presently working on a fix. (07/31/2024: 8:35 PM ET)
UPDATE: Intuit reports that the payment processing issues QuickBooks Desktop users were reporting have now been resolved. (07/31/2024: 9:45 PM ET)