This isn't the kind of experienced I want you to have, RobHere. 

I'll share information about trying to link a merchant services account in QuickBooks Online. I also appreciate you for providing screenshots and detailed information about your concern.

As shared above by my colleagues, the error "There was an error communicating with Quickbooks Payments Service. Please try again later" is still tagged as an ongoing issue. We are unable to provide a specific time frame on when this will be fixed.

 In the meantime, you can process ACH in the Merchant Center by going to Processing Tool > Accept an E-Check.

Also, I'd suggest reaching out to our Customer Care Team, so you'll be added to the list of affected users.

To reach them, click this link for details:  Contact Payments or Point of Sale.

Reach out to me if you need further assistance when working in QuickBooks. I'll be glad to lend a helping hand. Have a great day!