Symptoms

When on the Planning Console and if you try to use the Search Box, you see "Loading Failed"

Release

London Patch 3

Cause

The Project Portfolio Suite with Financials plugin has not been activated in your instances.
This plugin adds the $pmview UI page which as replaced the deprecated pc_gantt UI page.

Resolution

Activate the Project Portfolio Suite with Financials plugin

Additional Information

Please see the following documentation regarding the plugin: 
https://docs.servicenow.com/search?fo=no&q=Project+Portfolio+Suite+with+Financials&labels=2