Update (4/24/18 10:30 PM): We have removed the temporary restrictions described below, which were in place since this morning.
As a short-term way to resolve a server issue that we had on Monday (4/23/18), we have had to add a restriction (at least for now) that a teacher cannot view a project when a student has it open, and vice versa. The message you will see if you try to open a project that is currently already in use is:
When a student logs out (via Options > Sign Out) or navigates to a different project on their Projects screen, it will clear the flag on the project and allow you to open it. If the student has just closed the browser without logging out, the lock will remain on that project for an hour, after which the lock will be released and you will be able to access it (sorry, we know this is problematic, but better than the server going down!).
Until we can put less restrictive logic in place, please try to remember to use Options > Sign Out whenever you are leaving NoodleTools.
This change was a (necessary) very-short-term emergency measure that we needed to implement, but we are now working on a better solution that will not restrict access like this. We will be putting this in place soon (this week).