hey siri doesn't work when bluetooth is enabled

You don’t have any other iOS devices in range of your voice that are connected to the same Apple ID do you? This symptom is what I get when other devices are within range and they respond first. Usually it’s my a Watch when I inadvertently have twisted my wrist in a way that it wakes the screen and then picks up me saying “Hey Siri”.

You might just simply have to go in and re-record your voice for hey Siri. Going to the settings on your phone and you will find the Siri tab. If it is already on, toggle it on and off again

I’m in exactly the same position. Since the iOS 11 upgrade, Hey Siri wakes Siri up when I’m connected via Bluetooth in my car but I can’t ask Siri to then do anything and it goes back to sleep. I used to be able to call contacts, send messages, etc. without touching my phone while I’m driving. This is crazy. I’ve unpaired and paired the phone to the car several times to I don’t think it’s that. Any other ideas will be gratefully tried

Get help with Siri

• If "Hey Siri" isn't working, make sure that Allow "Hey Siri" is turned on under Settings > Siri.
• Siri might say, "Sorry, I'm having trouble connecting to the network," or "Try again in a little while." This is probably a network issue. Check your Internet connection and try again later.
• When you're using Siri to dictate, dictation is limited to about 30 seconds.
• To see a list of what you can ask Siri, press the Home button and ask "Siri, what can you do?" Or press the Home button, then tap the question mark in the lower, left-hand corner of the Siri screen.

If Siri isn't available, or doesn't understand or respond to questions

Before you try these steps, make sure that your device works with Siri. After each step, see if Siri is working.

1. Make sure that your iOS device has an Internet connection through Wi-Fi or cellular data.
2. On your iOS device, make sure that Siri is turned on under Settings >Siri.
3. Restart your iPhone, iPad, or iPod touch.
4. On your iOS device, go to Settings > Siri and turn off Siri. Then turn it on again.
5. If you're using an iOS device, try to use Siri with a headset. If Siri only works when you're using a headset, get help with the microphones on your device.
6. Contact Apple Support.

If Siri doesn't make a sound when you hold down the Home button

If you have an iPhone 6s or later, or an iPad Pro (9.7-inch), you won't hear a chime when you hold down the Home button because you can talk to Siri as soon as you begin pressing the Home button. You'll only hear the chime when you use headphones or Bluetooth.

On other iPad and iPod touch models, Siri will chime when it's time to ask a question. If you have an iPhone 6 or earlier with iOS 9 or later, Siri will vibrate instead of chime.

I thought that too! I have an iPad Pro on the shelf and my apple watch. I powered them off and even unpaired, same thing. I have a case open with apple care to see what's going on - but again, the most maddening part is there has been no change to where the phone normally lives. Still happening in my bedroom where I used it to set alarms and control lights all day 😟

I have just been having this issue with hey siri on ios 11.03 - WILL Not work unless I turn off bluetooth...

Download the new Apple Support app on your phone. They should be able to help

Nice