Problem while uploading the sketch.

Arduino: 1.8.5 (Windows 8.1), Board: "Arduino/Genuino Uno"

Sketch uses 2158 bytes (6%) of program storage space. Maximum is 32256 bytes.
Global variables use 52 bytes (2%) of dynamic memory, leaving 1996 bytes for local variables. Maximum is 2048 bytes.
avrdude: ser_open(): can't set com-state for "\.\COM6"
An error occurred while uploading the sketch

This report would have more information with
"Show verbose output during compilation"
option enabled in File -> Preferences.

Does this make sense to anyone?

And did you turn on VERBOSE as it suggests ?
It is in the Preferences.

You can then copy that full error message over here to give people a chance to help you.
BTW please use code tags ( </> ) to post error messages and code etc.
Make it a lot easier on everyone.