Thanks for letting me know about this, @russkostin.
I'm here to help share some information about QuickBooks Payments and get you pointed in the right direction.
There various possible reasons why an ACH transaction was disputed. To verify the current status of your transaction, I'd suggest reaching out to our Merchant Services Team. They have the ability to pull up your account securely while the Community is a public forum. This way, they'll be able to discuss further the main reason as to why the ACH payments were disputed.
Also, here are some articles that you can check out about handling ACH transactions in QuickBooks Online:
Please let me know, if you have any other questions with QuickBooks Payments. I'll be around to help you out. Have a great day.