Why won't Siri hear my voice when I say "Hi Siri"

Hey Siri doesn't work

Go to Settings. Tap Siri & Search. Turn off Listen for "Hey Siri," then turn it back on. When the Set Up "Hey Siri" screen appears, tap Continue.

If "Hey Siri" isn't working on your iPhone or iPad - Apple Support

Try “Hey Siri” not “Hi Siri”

and retrain it if necessary by turning Hey Siri off then back on