Not sure what the issue is as i was able to download and open the files. Perhaps it could be a version issue although i am not sure yet.
Christopher Lucskay can you share the error message on the pop up?
Please contact me on the mendix community slack channel so I can try resend you the original files.
Please can you move your project directory to be somewhere directly on your C drive, something like C://Mendix/Fitness-tracker.
Let me know if this works!