Properties Inspector Panel unavailable

My students are working on a project and suddenly find that the Properties panel will not allow them to make changes to their websites.  They can open the panel, but cannot click on anything in it.  The educational software they are using (which is designed to mirror tasks from the certification exam) shows easily clicking on it to chage the background image of their nav bar, but none of them are able to do so.  Honestly, I certified on an older version of DW, so I occasionally struggle, but I have done all of the troubleshooting I can think of.  Does anyone have any ideas for why they may all be having the same issue with this feature?  We've reached a stand still.