According to the Nikon Support Webpage:
When you see Err
on the control panel, LCD monitor or viewfinder of your digital camera it refers to a camera malfunction. Try the following:
Remove all accessories from the camera.
Install a freshly charged battery into the camera.
If your Nikon camera offers resets such as the two-button reset or
a hardware reset please follow those instructions provided in the
If these steps do not resolve the Err message we recommend having a
Nikon Authorized Repair Technician evaluate the Nikon camera. Click here
for repair information.
If you have additional questions, you can look up answers directly on the Nikon Suport Webpage below:
I hope this helps - and good luck!