Hi Kim, Laegwen and mintlemonade tips are still good and easier alternatives to camera lucida.
I suggest you to have a look online, there are many tips about how to fix that error message on your back camera "for android", which is your operating system. Somebody says that you need to restart your phone or soft reboot it and that's it, but I use apple devices so I can't really tell. Try also the free app for android called "Trace and draw" which works out as CamLucida, though if you already tried "Artist eye", with no success, probably it won't work either. Maybe if you bring your phone where you bought it they may help you.... Or maybe asking to a teenager will be even quicker!