From the KB - Parents see message "Not eligible for auto-pay" when trying to configure Auto-pay:

In a multi-parent household (two or more parents or guardians) the message indicates another parent has configured auto-pay for the student. Parent A cannot edit or remove auto-pay configured under Parent B.

This is just not realistic in most cases - families generally want either parent to be able to log in and make payment arrangements, including the ability to make changes if needed. This just further de-incentivizes families from using the online payment system which is already a problem.

Restricting access for auto-pay editing should be an option only for when needed ex divorce, 3rd party payers, etc.