Recently, I was tried upgrading my sample site from 7 to 10. Everything looked like it had upgraded and worked as expected until I tried to load the editor. When I tried to view the editor nothing loaded! Using Chrome's, 'Inspect' option, within the console I saw this error:

episerver_label_of_undefinied_1

In How To Render Custom HTML For Episerver Properties I briefly discussed the contents of the 'modules' and 'modulesbin' folders.

The modules folder is the place where the core Episerver framework files get installed. As the editor wasn't working I assumed something had gone wrong in the update process. To fix the issue I deleted everything within my modules folder and in the Nuget 'Package Manager Console' I re-installed Episerver, using

When issues like this have happened in the past I've always found it a good idea to close the solution, perform an IIS reset and clear my Temporary Internet files. After doing this Shell.zip was re-added into the 'Shell' folder and CMS.zip was re-added into the 'CMS' folder (within '_protected' in the modules bin). After opening Episerver in an incognito mode tab, the editor worked again!