Hi Jose,
Have you tried rebuilding the search solr index?
This will be on the presentation machine, in data/solr-indexes/search inside your opencast directory. Stop the opencast service on that machine and move the whole search folder somewhere safe (in case things go wrong you can just move it back later). When you restart the opencast service it should regenerate the solr search index. It can take a while if you have a lot of recordings but you should see things happening in the log.
Thanks,
Paul.