No items appear in edit tree. I get ajax errors code 500

Hi,

When I run the CMS, I am not seeing items in the ajax tree. When looking at the JavaScript console, I see a long string of 500 errors. These are some of them. Any idea of what is going on and how to fix it?

http://localhost:59458/EPiServer/Shell/8.5.1.0/ClientResources/EPi/shell/ui/nls/en-us/episerver.shared.js

http://localhost:59458/EPiServer/CMS/8.5.1.0/ClientResources/epi-cms/nls/en-us/episerver.cms.js

http://localhost:59458/EPiServer/CMS/8.5.1.0/ClientResources/epi-cms/nls/en-us/contenttypes.js