iPhone 6/Plus can't connect to Alpine stereo

Not sure, since you do not mention it, but if this is a Bluetooth connection you are trying to make, then look at this support document iOS: Troubleshooting Bluetooth connections - Apple Support and this one as well. iOS: Third-party Bluetooth accessories - Apple Support

What is happening? What do you see on the screen? Have you contacted Alpine to see if the radio supports the iPhone 6 and iOS 8? Have you contacted the vehicle manufacturer, if this is a stock vehicle radio to see what they have to say about it being supported?

Hi I have exactly the same problem since I upgraded to an iPhone 6 - my iPhone 4S on IOS7.x worked perfectly.

My headunit is an alpine CDE-136BT

My phone finds the head unit, but when I try to connect it says 'unable to connect'

not being able to play music or answer the phone using bluetooth is quite an annoyance to say the least.

I suspect that your problem is the head unit is expecting your iPhone 4S, not the 6. You need to go into the menu of the Alpine unit and make sure that the old phone pairing is removed from the unit. Since the iPhone is finding the head unit and when you attempt to connect it is failing, shows that the Bluetooth on the phone is functioning.

Does your iPhone connect via Bluetooth to any other Bluetooth device (headset, speakers, a photo kiosk)? If the answer is yes, then there's nothing wrong with the Bluetooth on your iPhone. The issue is with the Bluetooth accessory.

agree with the suggestion. it is a new phone so new pairing to the Alpine is require.