Spotify - Still a Problem

I installed Volumio 1.51 on a RPi B+

I then installed the packages build-essential and wiringPi library using apt-get install

Spotify does not start.

Output of pstree:

pstree
init-±avahi-daemon—avahi-daemon
|-dbus-daemon
|-2*[dhclient]
|-login—bash
|-minidlna
|-monit
|-mpd—4*[{mpd}]
|-nginx—nginx
|-nmbd
|-php5-fpm—5*[php5-fpm]
|-player_wdog.sh—sleep
|-player_wrk.php
|-rpc.idmapd
|-rpc.statd
|-rpcbind
|-shairport—{shairport}
|-smbd—smbd
|-sshd—sshd—sshd—bash—pstree
|-upmpdcli—7*[{upmpdcli}]
|-winbindd—winbindd
`-wpa_supplicant

Log File /var/log/spopd.log:

[ERR ] Can’t load sox audio plugin: libspop_audio_sox.so: cannot open shared object file: No such file or directory

I disabled Spotify, rebooted, enabled Spotify, rebooted, but the problem remains.

I am using a Spotify Premium account

Any recommendations?