If you have lost progress in a course, it could be due to one of the following reasons:
You are logged into the wrong account:
You may have two or more Codecademy accounts created with different emails. You may have created multiple accounts using your most common email addresses. It is also possible you initially logged in by entering your email address and password, and then mistakenly logged in a second time via a third party (i.e. "Sign in with Google" button). Or vice versa. This will essentially create two accounts for you - the second of which won't have any of your progress from the first account. You can fix this by logging back with your first account.
The Course or Path has been updated:
The Codecademy Curriculum team aims to keep all content up-to-date. Any and all course and path updates will appear in the notification bell in the top righthand corner of your "My Home" page. Changes will be explained in the Change Log - https://www.codecademy.com/articles.
We often introduce new content to our Catalog which can adjust your percentage of completion on a course. If any progress changes happen site-wide, we will publicize the changes by email and on our blog.
Progress was reset on a course or path with overlapping content:
Some of the material provided on Codecademy is shared between different courses, which means that resetting progress on one course or path could impact others as explained on the progress reset confirmation modal.
Use care when resetting. If your coursework has been reset accidentally, contact support by using the "Contact Us" button. We're happy to help restore your work as best we can.