Can't use custom library in Eagle
This isn't a direct answer, but you really shouldn't put your own libraries into the directory where the Eagle libraries are.  You don't know what will go there in future releases that might overwrite your files.

Create a directory for your own libraries.  Then add it to the library search path.

I go further and deleted the Eagle libraries directory from the libraries search path, since the Eagle libraries are of little use and it's easier to make your own parts than vetting their, even when theirs are acceptable.

As for why you library isn't showing up, I don't know.  I do what I described above and all my libraries show up all the time.