iPhone 7 has problems with Bluetooth, whether we are talking about connecting to cars or various accessories, and the iOS 10 operating system seems to have the same problems on various iDevices. Although almost everyone complains mainly that the iPhone 7 has problems with Bluetooth, the reality is that iOS 10 has the same problems and this probably affects the terminal.
In general, every release of a new product, or a major version of iOS, has generated problems of this kind with the Bluetooth connectivity of iDevices. Every year we go through the same situation and every year I make recommendations to solve Bluetooth problems, now with iOS 10, iPhone 7 and iPhone 7 Plus.
In general, these problems are transferred together with the data of a backup from one terminal to another, so that's why I generally recommend not to use backups after restoring or switching to another iDevice.
Forget Device, Ignore this device
A first attempt to solve the Bluetooth problems of iOS 10 and iPhone 7 is based on deleting the information regarding an accessory or car to which you have connected. This is done from the Bluetooth settings menu available in the Settings application, Configurations, by accessing the device with which you have problems using it at that moment.
Access the information regarding the settings of the problematic accessory by pressing the icon with a circled i, then choose the option Forget Device, Ignore this device. After doing this procedure, disable Bluetooth and reactivate the function, then try to connect again to the device that you previously could not connect to, or that does not work properly.
Resetting the network settings, Reset Network Settings
Another solution to solve, in general, almost any connectivity or GPS problems of iDevices is to reset the network settings. This option is available in Settings > General > Reset > Reset Network Settings, Configurations > General > Reset > Reset the network settings.
After using it, you will delete all the network configurations of your terminals, including saved passwords for Wi-Fi networks, or some settings for GPS and privacy. By deleting all these configurations, you can also solve Wi-Fi connectivity or Bluetooth connectivity problems, so it is a very good solution for many problems.
If these solutions do not help, then you will have to do a restore using iTunes, but you must avoid reusing a backup.