Dr. Pappas described
How to get your child's attention.
Then have your child repeat your instructions just to make sure he understands. Behavioral ignoring (non-compliance) differs from not turning to name at 9 mos., not waving "bye" back by 10 mos. Not sharing joint attention by 18 mos., not hearing you, being "hyper-focused" on electronic screens or preferred activities & other " can't" vs. "won't" issues.