I did not elect to receive the advance child tax credit in 2021. When I tell TurboTax that I didn't receive any payments, I expected my refund to change- but it did not?

The reason your refund didn't change when you marked that you did not receive any Advance Child Tax Credit payments is that when you start your return and/or add your dependents to your info, TurboTax assumes you will receive the full Child Tax Credit for each qualifying child.  It only needs to change if you report any amounts received.