I can help ensure you can connect your payment account successfully.
In QuickBooks, choose Customers and select Link Payment Service to Company File.
2. Enter the User ID and Password that you created when signing up and select Link Service.
3. Click Transfer.
4. When prompted, confirm the transfer of your service by clicking Yes, transfer.
If that doesn't work, try this alternative:
Open QuickBooks company file.
From the home screen, select Receive Payment. This opens the Customer Payment window.
On the Payment Method drop-down, select an appropriate card type (Visa, MasterCard, Discover).
Place a check-mark in the Process credit card payment when saving check box.
On the pop-up window that appears, place a check mark next to Link to an Existing Merchant Account then click OK.
Log in with your username and password linked to the account.
However, if you still can't connect your payment account to QuickBooks, I'd suggest contacting our Merchant Services Team. They have all the necessary tools to isolate this further and help you successfully connect and take credit card and ACH payments from your customers.