Searching Search US Core Implementation Guide (All Versions) is directed to site:C:\inetpub\wwwroot\hl7\implement\standards\FHIR\us\core (and fails).

Repro: 

• navigate to https://www.hl7.org/fhir/us/core/
• click on the hourglass in the top right (or the Search link in the footer)
• you are taken to the following page: https://www.hl7.org/fhir/us/core/searchform.html

• type some text into the search and click the hourglass to submit
• you receive the following result:
  

Note, if you select a specific version to search, it works correctly.