The bootloader is apparenlty supposed to be on a different port. Here’s the verbose output when trying to flash:
Arduino: 1.8.5 (Windows 7), Board: "Keyboardio Model 01"
Sketch uses 15828 bytes (55%) of program storage space. Maximum is 28672 bytes.
Global variables use 1470 bytes (57%) of dynamic memory, leaving 1090 bytes for local variables. Maximum is 2560 bytes.
Forcing reset using 1200bps open/close on port COM36
PORTS {COM1, COM36, } / {COM1, COM36, } => {}
PORTS {COM1, COM36, } / {COM1, COM36, } => {}
PORTS {COM1, COM36, } / {COM1, COM36, } => {}
PORTS {COM1, COM36, } / {COM1, COM36, } => {}
PORTS {COM1, COM36, } / {COM1, COM36, } => {}
PORTS {COM1, COM36, } / {COM1, COM36, } => {}
PORTS {COM1, COM36, } / {COM1, COM36, } => {}
PORTS {COM1, COM36, } / {COM1, COM36, } => {}
PORTS {COM1, COM36, } / {COM1, COM36, } => {}
PORTS {COM1, COM36, } / {COM1, COM36, } => {}
PORTS {COM1, COM36, } / {COM1, COM36, } => {}
PORTS {COM1, COM36, } / {COM1, COM36, } => {}
PORTS {COM1, COM36, } / {COM1, COM36, } => {}
PORTS {COM1, COM36, } / {COM1, COM36, } => {}
PORTS {COM1, COM36, } / {COM1, COM36, } => {}
PORTS {COM1, COM36, } / {COM1, COM36, } => {}
PORTS {COM1, COM36, } / {COM1, COM36, } => {}
PORTS {COM1, COM36, } / {COM1, COM36, } => {}
PORTS {COM1, COM36, } / {COM1, COM36, } => {}
PORTS {COM1, COM36, } / {COM1, COM36, } => {}
Uploading using selected port: COM36
C:\Program Files (x86)\Arduino\hardware\tools\avr/bin/avrdude -CC:\Program Files (x86)\Arduino\hardware\tools\avr/etc/avrdude.conf -v -patmega32u4 -cavr109 -PCOM36 -b57600 -D -Uflash:w:C:\Users\Bjorn\AppData\Local\Temp\arduino_build_897959/Model01-Firmware3.ino.hex:i
avrdude: Version 6.3, compiled on Jan 17 2017 at 12:00:53
Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
Copyright (c) 2007-2014 Joerg Wunsch
System wide configuration file is "C:\Program Files (x86)\Arduino\hardware\tools\avr/etc/avrdude.conf"
Using Port : COM36
Using Programmer : avr109
Overriding Baud Rate : 57600
avrdude: ser_open(): can't open device "\\.\COM36": The system cannot find the file specified.
avrdude done. Thank you.
Problem uploading to board. See http://www.arduino.cc/en/Guide/Troubleshooting#upload for suggestions.
This report would have more information with
"Show verbose output during compilation"
option enabled in File -> Preferences.