ACH transactions take 3-5 business days to be notified of success or failure. Once successful, it'll take another 1-2 business days to be paid out to your bank.
If the payment currently says pending, the transaction has not yet been approved. Once it pops over to "Charged" it will be 1-2 business days until it's in your account.
When created, ACH charges will have the initial status of pending that is reflected in the Billing section of a project
Over the 3-5 day period, the payment will either transition to succeeded or failed depending on your clients' bank.
Successful/Confirmed ACH payments will then be scheduled for automatic Outbound Transfer.
Your client will see the payment reflected on their bank statement 1-2 days after creating the charge. (Your customer will know the payment succeeded before the bank notifies Stripe.)
The payment will hit your account 1-2 days after succeeding.
Failures can happen for a number of reasons - insufficient funds, a bad account number, or the customer disabled debits from their bank account. You will be notified if a client's payment does fail.