What happens if parents cannot get a reaction from the sleeping child?

What happens if parents cannot get a reaction from the sleeping child, do go ahead anyway or try later?

head and shoulders photo of Joane Goulding founder of the SleepTalk Method

A. If the parent doesn’t observe a transition response, just continue anyway.

The deep unconscious will still hear, even if the child is in a very deep sleep or Delta brainwave frequency.