My child's mouth moves plenty, but no words come out. Life works even without them talking.

The more skillfully those around them read their needs, the less a "need to talk" arises. The trick is to build "small gaps that make them want to communicate" into daily life. 1) Don't anticipate everything in request situations; wait a beat with "do you want to?" 2) Talk to them with gesture plus words. 3) Use onomatopoeia (slowly, in short words). 4) Whenever your child sends any signal, respond instantly, in whatever form. Language grows on five foundations: the ability to distinguish and remember sounds, attention, body and senses, relationships with people, and comprehension. Not missing the moment your child reaches out, and responding, is the surest shortcut.