"Invalid response"

Check your USB connections

If you see error 4005, 4013, or 4014, learn what to do. If you see one of the errors below, you might have a USB connection issue:

• 13, 14, 1600, 1601, 1602, 1603, 1604, 1611, 1643-1650
• 2000, 2001, 2002, 2005, 2006, 2009
• An error message that includes, "invalid response"

Use these steps to see if the issue is with your USB cable, USB port, or computer. Try again after each step:

1. Use the USB cable that came with your device. If you don't have it, try a different Apple USB cable.
2. Switch to a different USB port on your computer. Don't plug into your keyboard.
3. Plug into a different computer.
4. If you still see the error, you can check for other USB issues, issues with third-party security software, and issues with hardware.

If the issue continues, contact Apple Support.

Get help with iOS update and restore errors - Apple Support

I'm sick and tired of having Itunes problems. Have had problems pop for years and years. Now i'm getting the invalid response, I have tried 4 different usbs/uninstalled itunes, restarted everything. Apple cannot make a solid product. Their usbs are designed to break in a few months, itunes is just garbage, and the music updates they do for the iphone are not sleek or easy to use whatsoever. If Itunes didn't have such a monopoly on the music market I would gladly take my business elsewhere.

Thanks Allen for contributing new helpful advice. You literally just copy and posted the first thing that pops in google when you type "Itunes invalid response".