Is it normal for them to take almost a month to accept a payment?

I am on their payment plan.
I did make a much larger payment on the 8th of this month.

So far I have not seen the cash taken out of my account. I did do a test to see if it’s maybe because it’s a large amount it’s taking a while so I made a $10 payment and that was taken then next day.

I did check the confirmation number on the email receipt and it said “Your payment has been processed. We are unable to modify or cancel your payment at this time. (You have the option to modify or cancel any payment until 11:45 P.M. ET two business days before the payment date.)”

I did call my bank and they said they can’t do anything and I tried calling the IRS after work but its either I get customer service who transfer me to someone else and I get hung up or I get no one….

Should I wait one more week? Is this normal. I really don’t want to make another payment because I’m very close to be done paying this off but what’s the best option?