Once you have connected successfully Google Play Music, you will be able to retrieve elements under "My Library" on Soundiiz.
Tracks, Artists and Albums retrieved here are taken from your "Thumbs Up" tracks playlist Google Play Music.
That means if you are doing a "Thumbs Up" on a GPM track, you will also see the Album and the Artist here on the Soundiiz list.
What about my saved tracks collection Google Play Music ?
We are able to retrieve them up to 50 000 tracks and are under a generated playlist called "Library Tracks". If you have connected Google Play Music to Soundiiz you can follow this link.