Thank you for posting here in the Community page and clarifying on the error you're getting. I'm here to help provide information and a possible fix for this concern.
There are several experiences when some customers are getting this error. Here are the scenarios you may relate to:
Scenario 1: Error (-32122) when using the Receive Payment section. Some customers who clear the browser's cache rid this error. This deletes files that are affecting the browsing performance.
Scenario 2: Business Validation Error. Unexpected Internal Error (-32122). The card declines due to the merchant attempting to record a Sales Receipt in QuickBooks Online that has the same number of one that already exists.
You can run and customize a Sales by Customer Detail report to track Sales Receipts lists only. Then, determine and delete duplicate Sales Receipt that's causing the error message.
Go to Report.
Enter Sales by Customer Detail report on the search bar.
At the upper right corner, click the Customize button.
On the Rows/columns, click change columns, then select the columns that are needed to show in your report.
On the Filters tab, choose the Transaction type.
Put a check mark for Sales Receipt.
Click Run report.
Scenario 3: Business Validation Error. Unexpected Internal Error (-32122). Occurs when QuickBooks connections need to be validated by the system. To get this fix, you can post your concern in our Intuit Developer Forum and interact with different experts to get the help you need.
In your case, you may need to cut a check using a private browser or an incognito window. You can use either of the following shortcut keys:
Google Chrome, press CTRL + Shift + N
Mozilla Firefox: press CTRL + Shift + P
Internet Explorer: press CTRL + Shift + P
Safari: press Command + Shift + N
If it works fine using a private browser, you may need to clear the cache of your regular web browser. Also, switching to another supported browser can help us narrow down the cause of this unexpected behavior.
Stay in touch if you have any other QuickBooks concerns by adding a comment below. Wishing you continued success!