Q: it wont let me connect to itunes with my iphone 6. my iphone, itunes and mac are all up to date. it keeps saying that there is an invalid response

Invalid response points to USB issues ...

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