After updating to version 2.64, you must update the web.config file. By default, this file can be found in C:Program Files (x86)ValuekeepValuekeep-UniverseHostWeb.config.
1. To allow for editing reports with complex data sources in Report Designer, add this configuration:
<appSettings>
(…)
<add key=”aspnet:MaxJsonDeserializerMembers” value=”150000″ />
</appSettings>