Jul 16, 2019 07:18 PM|bruce (sqlwork.com)|LINK
if hosted by IIS there is a web.config that configures the core hosting module. The error just says if dev mode is enabled you will get more error info. Your just rebuild the app to always use the developer error page (just take out the if).
to help more we need to know the hosting environment, windows, linux, etc. if II which version of the core module yo are using.