printer does not print ink even though it is detected

USB printer model Epson ET-4500 detects the desktop it is connected to, but when printing a piece of paper the printer only spits out plain paper with no ink.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: cups 2.1.3-4ubuntu0.4
ProcVersionSignature: Ubuntu 4.4.0-127.153-generic 4.4.128
Uname: Linux 4.4.0-127-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.18
Architecture: amd64
CurrentDesktop: XFCE
Date: Thu Jun 7 17:37:23 2018
InstallationDate: Installed on 2016-10-12 (603 days ago)
InstallationMedia: Xubuntu 16.04.1 LTS "Xenial Xerus" - Release amd64 (20160719)
Lpstat: device for EpsonET-4500: usb://EPSON/ET-4500%20Series?serial=573937593033313180&interface=1
MachineType: Dell Inc. OptiPlex 780
Papersize: letter
PpdFiles: Error: command ['fgrep', '-H', '*NickName', '/etc/cups/ppd/EpsonET-4500.ppd'] failed with exit code 2: grep: /etc/cups/ppd/EpsonET-4500.ppd: Permission denied
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.4.0-127-generic root=UUID=03b2da64-2d26-4809-b705-f42bd7d8a473 ro quiet splash vt.handoff=7
SourcePackage: cups
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 08/11/2010
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A05
dmi.board.name: 0C27VV
dmi.board.vendor: Dell Inc.
dmi.board.version: A02
dmi.chassis.type: 6
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvrA05:bd08/11/2010:svnDellInc.:pnOptiPlex780:pvr:rvnDellInc.:rn0C27VV:rvrA02:cvnDellInc.:ct6:cvr:
dmi.product.name: OptiPlex 780
dmi.sys.vendor: Dell Inc.