Google Play Music songs don't show up -- but only on one of the devices I own I got a few albums uploaded, all the songs (the full albums ) show up in my tablet ( Samsung S ), also they show up in the web player and in my old Samsung S3. But my S4 with lollipop just shows two or three songs of each album.

I already tried refresh, also I changed the storage,  I cleared the data, and the cache. But everytime I log and browse the albums just two or three songs shows up.

Edit.
Also I wiped out the whole system and even the dalvik cache.
I was having the same problem and have a case open with Google on this issue.  While I have not heard back from them yet, I continued to investigate this issue myself and may have found a solution.  What I did was open Goolgle Play music from my browser on my laptop.  In settings, under my devices I deactivated my Android phone (Galaxy S5).  On my phone I did a Force stop of the application and cleared any data.  Then I restarted the app and did a refresh just to force it.  

Before I did this, several artists were missing and many songs as well.  for example my phone only showed 8 Beatles songs.  Now I am showing 256.  On my laptop, I still show more songs 269, but it a heck of a lot better.  Other artists I checked show up as well. 

I believe this all started after I did a full wipe of my phone due to battery issues with the lollipop upgrade.   Hopefully this helps.

MS