Why is plex not detecting the files i have?

Am not sure if am in the right place but when i try to add a library everything’s good not until i select the folder i have the movies in, i can see the movies i have but they are in light grey as if they aren’t compatible and when i add the library there is nothing in it.
Why is this happening?

Most often due to permissions. Make sure that the user under which Plex runs as has the correct access right.

I have also seen this happen when the filenames are “Just not right” try making the file name as simple as possible to test if it shows up then.