I can't get my Hey Siri to work

I can't get my hey siri to work! i say hey siri but it won't pick up my voice. i've tried resetting it but it doesn't help anything! i am crying because this is a new phone. it's like my phone is not picking anything up but when i hold the side button it works just fine!! PLEASE HELP ME!!!!!!!!!!!

[Re-Titled by Moderator]