After updating to version 2.78, you must update the web.config file. By default, this file can be found in C:\Program Files (x86)\Valuekeep\Valuekeep-Universe\Host\Web.config.
1. To retrieve the translation files used in the Planner, add this configuration value:
<staticContent>
(…)
<mimeMap fileExtension=”.json” mimeType=”application/json” />
</staticContent>