iPhone won't connect to computer

Connect iPhone to Computer / Mac

Use your USB lightening cable --> Resolve USB-related alerts in iTunes - Apple Support

If unable to connect --> If iTunes doesn't recognize your iPhone, iPad, or iPod - Apple Support

Use genuine cable --> Identify counterfeit or uncertified Lightning connector accessories ...

You may get better and prompt responses if you may kindly provide the iPhone Model that you have and the iOS version if it is known to you.