Hi @khairulanam, let me help you with this.
Can you share your lab ID with me ?
In your assignment, you’ll see a “Help” icon on the top right, once you click on it a panel will open Your lab ID will be shown at the bottom.
Can you be a little more specific about what your problem is? If you just mean that it looks like your previous work on this one particular assignment is gone, that probably means that the staff has published a new version of the assignment. In that case, you can find your previous work by clicking “File → Open” and looking around. You should find another notebook with the date and time interpolated into the name. Open that one in parallel with the new one and then copy/paste over your work to the new clean version.
But if that explanation is not relevant, please show us the actual error you are getting.