Document preview not working in Search

Hi there - we are trying to implement hybrid search between SP 2013 and Office 365. We have a single Office Web Apps server and it appears to functioning correctly.  We have a two on-prem farms, Prod and Test, both pointing to the same Office 365 tenant for hybrid search.  For troubleshooting purposes, I haven't filtered out any of the search results on either of the two on-prem farms.  Here is the issue - if I do a search from either farm, I am able to do a document preview for content from the Test farm but not from the Prod farm.  Office 365 results also shows the document preview correctly.  The Prod search results give me the option to select Edit.  I can also click on the document library where the item is stored and do a document preview from there - just not from the search results.  I originally thought it might be something to do with a display template but since it works for the Test and Office 365 results when doing a search from either the Test or Prod farms, I ruled this out.  Please let me know if you have any ideas.  Thanks!!!