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.
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.