Hi Kath,
Try the following:
1. go to Menu >settings scroll down to "Restore Default Settings"
2. press Ok, select restore all but WiFi and Fax Settings, press Ok
If that doesn't work, using the following picture as a guide, I am not sure as I'm not familiar with your particular model but if you look into the paper feeder (#2 in the picture) you may be able to see the sensors in there. In my printer they are spring loaded switches that are pushed up when the paper is inserted.
[image|747888]
Hopefully this is of some help.