Coveo Zero Results Issue

First, based on project requirements on Coveo version you have installed all Coveo components, hooked up your sitecore to use Coveo and all is well on Diagnostics. All components are Green.

Now, you drop or use newly and successfully built index for your search queries, you get zero results back.
Why would it return zero results, is it picking incorrect index? Are my configurations fine? Then you go the good old CES console to see if there are any errors.  Except for query returning 0 results, there are no errors.
But, I note this on the CES console –

Query (@fz95xlanguage76852==”en”) (@fz95xpath76852==3ab17f3f16be4a018105ecade4380857) (@fz95xtemplate76852==f5cc486b394c40ff8320480ec7c650a7) performed by extranetAnonymous [Sitecore Security Provider for blah-blah.com]. 0 results in 0.016 seconds.

I copied the query and ran it in Index Browser on CES Administration tool.  It did return loads of results.  So, it is not data, it is there for sure and query is correct as well.

Seems like the query was run by Anonymous user.  So, few check points to ensure this is not permissions issue.

  1. Ensure extranet/anonymous user on sitecore instance have read permissions on the content tree 
  2. Go to Index Browser and run the query above, go to any of the search results and look for permissions tab under Details.  It should show who all have access to this item.  
  3. You should see ‘Anonymous’ there.  If Anonymous is not there, that could be a problem and which is why the results come back as ‘0’.  I did not see this user in permissions and started scrambling on what I can do to fix this.  I came across the below blog 
The problem stated there looked exactly like mine.  I did the last step which is to clear caches on Details Tab under content security and once I did that, I could now see anonymous under permissions in individual documents. 
All is well and no more empty results. 
Query (@fz95xlanguage76852==”en”) (@fz95xpath76852==3ab17f3f16be4a018105ecade4380857) (@fz95xtemplate76852==f5cc486b394c40ff8320480ec7c650a7) performed by extranetAnonymous [Sitecore Security Provider for blah.com]. 203 results in 0.031 seconds.