Hi 123321123321,
With the QuickBooks Online US version, we can only process invoices through Credit Card and Bank Transfer.
Can you provide a screenshot as to where you see the option to process an auto-debit on the invoices?
It would help me give the correct process of the auto-debit.
On the other hand, we can process an ACH Payments by setting up QuickBooks Payments.
I've also added this article that talks about taking and processing payments: Take and process payments with QuickBooks Payments.
Let me know if you have other questions when setting up payments. Take care!