1. Go to Setup, Settings, Customers & Sales/ Receivables.
2. Select Invoice Payments and get the captcha error.
3. Go to Banking, Match Bank Transactions, and choose Upload to Bank Services.
4. Choose New Bank Account, then enter something in the Bank Name and Account type fields.
5. If you use foreign currency, pick a Currency.
6. Click OK.
7. You'll get a captcha window. Enter a code from the customer's email. 
8. If you get to the screen that displays "Import bank transactions", cancel and try invoice payments again.
    NOTE: The invoice payments option to download transactions will be back on after re-connecting. If the customer prefers to enter transactions manually, uncheck the box in the settings.
9. Go back to Setup, Settings, Customers & Sales/ Receivables, then Invoice Payments.
10. Click Set Up Invoice Payments. If the button is greyed out, close the company file and reopen it and try again.

If you're still having issues, contact customer support for assistance.