Can't scan using HP 3520 All-in-One

Installed printer at settings / printers using plus sign. HP-setup couldn't detect the unit.

Able to print to the unit but can't scan. Simple Scan doesn't find a scanner.

Basic system information:
Linux ToshibaLaptop 3.2.0-74-generic-pae #109-Ubuntu SMP Tue Dec 9 17:00:00 UTC 2014 i686 i686 i386 GNU/Linux

Checking Python version...
OK, version 2.7.3 installed

Currently installed HPLIP version...
HPLIP 3.14.10 currently installed in '/usr/share/hplip'.

Current contents of '/etc/hp/hplip.conf' file:
# hplip.conf. Generated from hplip.conf.in by configure.

HP-Deskjet-3520-series
----------------------
Type: Unknown
Device URI: dnssd://Deskjet%203520%20series%20%5BAE3AA9%5D._pdl-datastream._tcp.local/
PPD: /etc/cups/ppd/HP-Deskjet-3520-series.ppd
PPD Description: HP Deskjet 3520 Series, hpcups 3.14.10
Printer status: printer HP-Deskjet-3520-series is idle. enabled since Sun 21 Dec 2014 10:35:18 PM EST
warning: Printer is not HPLIP installed. Printers must use the hp: or hpfax: CUPS backend to function in HPLIP.