There are two different types of saved progress for Free Code Camp: your profile and your browser cache.
A list of your completed challenges is saved to your account in the FCC database. You can see the list of completed challenges by looking at your public portfolio. With a growing curriculum already over 1,400 lessons and a community of millions of people, FCC does not store every solution to every challenge in its database. When you complete a challenge, there is a modal that gives you the option to download your solution. This gives you the option to save a copy of any solution that you may want to reference later. There are some challenges which are classified as projects required for certifications. Your solutions to those can be viewed on your settings page.
Your in-editor code is saved in your browser’s local storage. Recent in-progress code from the challenge editor is also saved in your local browser cache when you run tests. If you are completing lessons and do not see your recent code, then your local storage has been cleared or something is preventing FCC from writing to your browser’s storage. This could be a browser setting, a privacy extension, or a browser version incompatibility. Especially as you get to more complicated challenges that may take multiple sessions, I strongly recommend saving your in-progress work outside of the browser cache.
If you are not seeing anything saved when you use freeCodeCamp, your login session may have expired or your browser may be preventing freeCodeCamp from writing to your cache. I suggest logging out, clearing your cookies, and logging in again. Certain privacy extensions or nonstandard browsers can also interfere with your freeCodeCamp experience.