keep getting 'failed to retire device in recovery mode, libusbrestore error: 2015' what can I do?

Hello,

Please refer to the following Apple Support document.

If you can't update or restore your iPhone, iPad, or iPod touch - Apple Support

The error you provide, 2015 does not appear in the Apple error list. At this point, since you followed the steps that zmclearan provided for being unable to update/restore, I suggest that you make a Genius Bar appointment at the nearest Apple Store to have Apple examine the device.