Students are restricted from completing assignments related to assembling the projects in the Build and Program Games with Arduino course until they pay (I require $2 from my students). I do this to ensure buy-in. Students who pay $2 almost always finish their projects.
If you do not want to require your students to pay for materials, let me know and I will put your group in the Payment Not Required grouping. This will allow your students to access all course materials without paying (although they will still be restricted from the assembly assignments until they complete the soldering safety quiz).