CoBlock codes of students reset?

I do not understand why I can not see the work of most of my students they did during the Christmas holidays on the space called “EF8 Projector V3.2 23_12_18” on my account with address, classes 4e1, 4e2, 4e3, 4e4. Some have completed the codes with CoBlocks, but I see codes not completed.
Thanks for your help.