Server Version#: 1.21.0.3616-d87012962
Player Version#: - just looking at the website
Very strange. I have tracks by Vandelux, Velvet Undergound etc. which are findable by searching, but not visible in the tracks list.
On the right Alphabet nav, the letter “V” is missing. I can see the song in a playlist where I added one of the V songs. Tried reloading the webpage again, still persists.
Songs are there in the folders. Id3 tags are correct etc.
So… are those full albums of those bands or are they maybe part of a compilation.
Even my “various artists” albums are showing under V. So it doesn’t seem to be a general issue that Plex ignores that letter 
There are individual tracks, from a variety of different artists. Well, V on the nav, and in the song list were showing up earlier when I first installed Flex and set up this server.
It just mysteriously got to this point. There is no custom filter or anything like that going on.
I just don’t know how to get the letter V back, or to see my V songs. . very mysterious.
I know the letter nav will hide a letter if there are too few tracks with that letter. For example, I only have one song by Queen, so Q doesn’t show, but at least the track isn’t hidden from the list.
Have you considered simply watching your library by artist and to open those “V” artists that way?
Q, U and V are also not showing for me.
I have 3 artists that start with Q, 3 artists starting with U and 3 (4 with Various) artists starting with V.
There appears to be 22 spots allocated along the right side of the screen, # and 21 letters, so 3 letters are dropped. A different 3 for Song, Album and Artist. 
