But at a guess, if you're saying that you don't see a project that you have previously created, I can think of a few possible reasons:
If you pick "In your web browser" - as shown in the screenshot - then you need to use the same web browser to access the project. If you use a different computer (or even just a different web browser on the same computer), then you won't see the project.
Reason 2 - You stored the project in your web browser, but cleared your browser storage
As above, when you create a project, you decide where you want to store it. If you choose "In your web browser" then all of the project details are stored in your browser storage.
If you use Incognito Mode or Private Browsing, then your browser will clear your storage when you close it - which will delete your project data.
Similarly, if you clear your browser storage, you will delete the project data.
Reason 3 - You didn't create an account to access the website
When you start using the site, you choose whether to create an account or just access the account using a temporary login using "Try it now"

If you try the site using a temporary session, as shown in the screenshot above, then all of your data is automatically deleted after four hours.