You can reset the progress by selecting specific users and their specific courses but if you want to reset all the courses’ progress together, there is an option too.
Steps:
1- You will find the Reset by user option in your WordPress admin area navigating to the LearnDash LMS menu ➡ Reset Course Progress ➡ Reset by Users tab.

2- Select Users you would like to reset the progress for.

3- Select Reset type

4- Select courses that you would like to reset for the selected users.

5- Press the Reset Button.

That’s it! ?
You just have reset the progress for the selected options.