It's nice to have you in the Community, @usermwever. Let me address your concern about adding ACH payment option in your invoices.

With regards to this matter, I recommend contacting the Merchant Services Support Team. They have specialized tools to review your account and assist you with adding this payment option to your invoices.

Furthermore, I've included this handy article so you'll have a guide to manually record invoice payments in QBO.

For future reference, you can review some of our answers to the most commonly asked Payments questions: QuickBooks Payments FAQ's. 

I'll be around if you need further assistance about managing your invoices. I'm always around here in the Community to help you. Keep safe and have a wonderful day!