Ask Siri is not active in my phone

Set up "Hey Siri" to help Siri recognize your voice

1. Go to Settings.
2. Tap Siri & Search.
3. Turn off Listen for "Hey Siri," then turn it back on.
4. When the Set Up "Hey Siri" screen appears, tap Continue.
5. Say each command that you see on your screen.
6. Tap Done.

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

Follow the Steps One after the other in sequence...

1. Settings > Siri & Search > Listen for "Hey Siri" [Disable]
2. Settings > Siri & Search > Press Home for Siri [Disable]
3. Next
4. Settings > Siri & Search > Press Home for Siri [Enable]
5. Settings > Siri & Search > Listen for "Hey Siri" [Enable]

Watch the GIF below