Please check the following:

• Make sure your ColorReader device is fully charged, then delete the ColorReader app from your mobile phone and restart your phone.
• Uninstall and reinstall the ColorReader app from the AppStore / Google PlayStore
• Make sure that the ColorReader app has the permission to access the location services from Android / iOS, as only this will allow the ColorReader app to use the Bluetooth functionality of your mobile phone.
• Next launch the ColorReader app, make sure your ColorReader device is still powered on to connect the ColorReader app to your ColorReader.

Please also read this when you use an Android mobile device:

• Turn on your device and go to the Android Bluetooth® settings. Make sure your ColorReader  is listed as the device available to sync up with. Don’t try to sync the ColorReader using the Android Bluetooth® settings.
• Now launch the ColorReader app, make sure your ColorReader is still powered on to connect the ColorReader app to your ColorReader.