Plex no longer picking up new movies loaded onto server

I’ve been using Plex media server for several years to run movies ripped from DVD’s onto a 5TB server. I have successfully loaded over 1300 movies, but just recently, Plex doesn’t show newly added movies despite my refreshing the library. The new media is loaded onto the same location as the 1300 movies, but Plex will not recognize them. Any hints?