There are two different types of saved progress for Free Code Camp: your profile and your browser cache.
Your completed challenges are all saved to your account in the FCC database. You can see the list of completed challenges and by looking at your public portfolio. The last submitted solution for challenges listed as projects can also be viewed from this 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. Because FCC rolled out a completely new application, the old cached values are no longer valid. This is the same effect you would have if you cleared your browser cache. If you are completing lessons on the new site, and do not see your recent code, then 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. This is a good opportunity to learn the ins and outs of your GitHub account, but you can also just save locally or use a service like repl.it which allows for versioning.
The forum and FCC are completely separate entities with different accounts. The platform that FCC uses for its forum (forum.freecodecamp.org) allows logging in with GitHub credentials. FCC (learn.freecodecamp.org) no longer supports logging in with GitHub credentials. All users must login using their email address.