Range needs the full volume and a good connection from your headphone jack to work reliably.
- Make sure Range is firmly plugged into your iOS device's headphone jack. You may need to remove your case to get it all the way in.
- If there is lint or dust in your iOS device's audio jack, it may interfere with its ability to read Range's data. Try cleaning out the audio jack and seeing if that solves the issue.
- Range draws power from your iPhone's audio jack — make sure the volume level of your iOS device is at the maximum level to allow it to be properly powered. If you have volume limits set on your iOS device, it won't be able to read Range's data. Check the volume levels in Settings → Music → Volume Control.
- Under iOS Settings → Accessibility, make sure that you do not have “Mono audio” enabled.
- Range also needs permission to use the microphone input in the headphone jack. Check in your phone's settings app that it's enabled. (Settings → Privacy → Microphone)
EU devices: Range is not guaranteed to work with iOS devices purchased in the EU. Unfortunately, due to EU regulations to protect against ear damage, Apple has locked the volume of many European models to lower than what the devices are capable of. Unfortunately, it's hit or miss — about 15% of devices do work, though about 50% of iPhone 3GS and iPad Mini Retinas in particular seem to work. If you have an iOS device purchased in Europe, you may have an additional setting under Volume Control called "EU Volume Limit" — please turn that off.
The only reliable way to get Range to work with an EU device is through "jailbreaking" (explanation and how to). Once your device is "jailbroken", install this tweak to remove the EU volume restriction, and your Range will work as intended.