Thanks for taking the time to scour our Community space for potential solutions. If you haven't encountered this yet, this solution will prove useful in resolving the payment processing issues, PCSLabTesting.

I appreciate you for performing the troubleshooting steps to get this error message sorted out. Let's make sure that your QuickBooks is updated to the latest release, so you'll have the latest features and fixes. Here's how: 

1. Close your company files and QuickBooks.
2. Open the Windows Start menu.
3. Look for QuickBooks Desktop, and then right-click the icon and choose Run as administrator.
4. On the No Company Open screen, go to the Help menu and select Update QuickBooks Desktop.
5. Select the Options tab and then choose Mark All, after clicking Save.
6. Go to the Update Now tab and click the Reset Update checkbox.
7. Once you're ready, choose to Get Updates.

Then, try processing a credit card again by following the steps below:

1. Sign in to the Merchant Service Center.
2. Go to Processing Tools and choose Charge a Card.
3. Complete the fields. Comments you add are only visible to you and the cardholder.
4. After you process the payment, you'll see a confirmation page.
5. Select Print, E-mail, Void, or Done.

If the same thing happens, we can open another company file to check if you're having a problem with only one file and not the program itself. Let me show you how:

1. In your QuickBooks, go to the File menu at the top left.
2. Choose Close Company.
3. In the No Company Open window, click the drop-down arrow in the Open a sample file icon.
4. Choose a sample file and click on it.

If it works, there may be a damaged data on the company file you've been working with. When this happens, you'll encounter the Payroll Alert - Update Now error again after doing the updates. We can run the Rebuild Data tool is built-in to fix any company file data issues. Just follow the steps and detail in this article: Fix data damage on your QuickBooks Desktop company file. We can also repair your software to fix any damaged component in QuickBooks. This also fixes any errors while using, installing, or updating QuickBooks. See the Repair your QuickBooks Desktop for Windows article for more details. 

When the update is finished, close and reopen QuickBooks Desktop. Then, click Yes to complete the process. Once done, restart your computer. If you have other questions about QuickBooks Payments, you may want to visit this page to find answers: QuickBooks Payments FAQ.

Feel free to update us after performing the steps as I want to ensure this is resolved for you. Please add a reply below and I'll get back to you. Take care always.