After upgrading the site from CMS 7.1 to CMS 7.5 and Find to 7.5.450.89 I don't get any files back in a unified search result.
The simplest query without any filters "SearchClient.Instance.UnifiedSearch().For("foo").GetResult().TotalMatching" returns 0.
When browsing the index the files are indexed as EPiServer_Web_Hosting_VersioningFile instead of my custom "GenericMedia" class. And I can't see "GenericMedia" anywhere in the type hierarchy in the index.
You might need to do a reindex if you haven't done that yet.
I have upgraded the media and have manually reindexed it and no difference...
Reindex = EPiServer Find Content Indexing Job
Or is there an other way?
What happens if you upload a new file? Still nothing? Do other media types show in in the index? If you have something like ImageMedia
Two things to check.