Teensy 3.6 test

Hi.

I am having difficulties executing tests using PlatformIO on my Teensy 3.6.
Initially I wrote my own test after reading the Unit Testing tutorial, but when I try to execute the tests with the board connected, it builds, uploads and starts testing but nothing more happens. When I press the reset button after 10 seconds, the the terminal output is the following,

`Testing...
If you don't see any output for the first 10 secs, please reset board (press reset button)

Error: Traceback (most recent call last):
File "c:\users\victo.platformio\penv\lib\site-packages\platformio_main_.py", line 109, in main
cli() # pylint: disable=no-value-for-parameter
File "c:\users\victo.platformio\penv\lib\site-packages\click\core.py", line 829, in call
return self.main(*args, **kwargs)
File "c:\users\victo.platformio\penv\lib\site-packages\click\core.py", line 782, in main
rv = self.invoke(ctx)
File "c:\users\victo.platformio\penv\lib\site-packages\platformio\commands_init_.py", line 44, in invoke
return super(PlatformioCLI, self).invoke(ctx)
File "c:\users\victo.platformio\penv\lib\site-packages\click\core.py", line 1259, in invoke
return _process_result(sub_ctx.command.invoke(sub_ctx))
File "c:\users\victo.platformio\penv\lib\site-packages\click\core.py", line 1066, in invoke
return ctx.invoke(self.callback, **ctx.params)
File "c:\users\victo.platformio\penv\lib\site-packages\click\core.py", line 610, in invoke
return callback(*args, **kwargs)
File "c:\users\victo.platformio\penv\lib\site-packages\click\decorators.py", line 21, in new_func
return f(get_current_context(), *args, **kwargs)
File "c:\users\victo.platformio\penv\lib\site-packages\platformio\commands\test\command.py", line 171, in cli
"succeeded": tp.process(),
File "c:\users\victo.platformio\penv\lib\site-packages\platformio\commands\test\embedded.py", line 52, in process
return self.run()
File "c:\users\victo.platformio\penv\lib\site-packages\platformio\commands\test\embedded.py", line 83, in run
line = ser.readline().strip()
File "c:\users\victo.platformio\penv\lib\site-packages\serial\serialwin32.py", line 275, in read
raise SerialException("ClearCommError failed ({!r})".format(ctypes.WinError()))
serial.serialutil.SerialException: ClearCommError failed (PermissionError(13, 'Enheden genkender ikke kommandoen.', None, 22))

============================================================

An unexpected error occurred. Further steps:

• Verify that you have the latest version of PlatformIO using
  pip install -U platformio command

• Try to find answer in FAQ Troubleshooting section
  https://docs.platformio.org/page/faq.html

• Report this problem to the developers
  https://github.com/platformio/platformio-core/issues

============================================================`

I then tried to use the calculator example, but the outcome is the same. It simply tries to run the test, but nothing ever happens.
I've also made sure I am using the latest version of PlatformIO.

What am I doing wrong?
Thanks in advance

Reproduce the failure with the unit-testing tutorial and the linked calculator example on a Teensy 3.6, then start from platformio/commands/test/embedded.py and the reported serialwin32.py traceback. Done means identifying why test output stalls or the serial connection fails and documenting the verified correction for this board and setup.