If you qualify for the Child Tax Credit you will still get it regardless of what you owe, but there is a bigger issue here.
As a condition of your payment plan you were obligated to keep all of your current taxes up to date.
You should pay off what you owe for 23020 right now if you can. If you cannot, I suggest you contact the IRS now and try to make some arrangement.
You can call toll-free at 1-800-829-1040 or visit a Taxpayer Assistance Center Local IRS Office .