I see a lot of post about people who cannot connect to the iTunes store on the IOS 11. I have this same issue however I can update all my Apps just fine. I am just unable to download apps or do any in app purchases. This is started on D-day of the IOS 11 beta release.
can't connect to iTunes store
My situation is weirder - my AppleID is associated with my iPhone but it won't let me use the same ID for iTunes - it will only accept a different ID. Just weird.
I reset Network Settings and that allowed me to login. I also had to turn on iCloud Playlists back on as well.