A print screen button doesn't work

When I push a print screen button - nothing happens, instead of taking a screenshot

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: xorg 1:7.7+19ubuntu14
ProcVersionSignature: Ubuntu 5.4.0-21.25-generic 5.4.27
Uname: Linux 5.4.0-21-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.11-0ubuntu26
Architecture: amd64
BootLog: Error: [Errno 13] Permission denied: '/var/log/boot.log'
CasperMD5CheckResult: skip
CasperVersion: 1.445
CompositorRunning: None
CurrentDesktop: XFCE
Date: Sun Apr 12 14:03:09 2020
DistUpgraded: Fresh install
DistroCodename: focal
DistroVariant: ubuntu
ExtraDebuggingInterest: Yes, if not too technical
GraphicsCard:
 Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller [8086:2a42] (rev 09) (prog-if 00 [VGA controller])
   Subsystem: Acer Incorporated [ALI] Mobile 4 Series Chipset Integrated Graphics Controller [1025:0459]
   Subsystem: Acer Incorporated [ALI] Mobile 4 Series Chipset Integrated Graphics Controller [1025:0459]
LiveMediaBuild: Xubuntu 20.04 LTS "Focal Fossa" - Beta amd64 (20200411)
MachineType: Acer Aspire 5734Z
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=ru_RU.UTF-8
 SHELL=/bin/bash
ProcKernelCmdLine: file=/cdrom/preseed/username.seed initrd=/casper/initrd quiet splash --- maybe-ubiquity
SourcePackage: xorg
Symptom: display
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 04/16/2010
dmi.bios.vendor: Acer
dmi.bios.version: V1.01
dmi.board.asset.tag: Base Board Asset Tag
dmi.board.name: Aspire 5734Z
dmi.board.vendor: Acer
dmi.board.version: V1.01
dmi.chassis.type: 10
dmi.chassis.vendor: Acer
dmi.chassis.version: V1.01
dmi.modalias: dmi:bvnAcer:bvrV1.01:bd04/16/2010:svnAcer:pnAspire5734Z:pvrV1.01:rvnAcer:rnAspire5734Z:rvrV1.01:cvnAcer:ct10:cvrV1.01:
dmi.product.family: Intel_Mobile
dmi.product.name: Aspire 5734Z
dmi.product.sku: Montevina_Fab
dmi.product.version: V1.01
dmi.sys.vendor: Acer
version.compiz: compiz N/A
version.libdrm2: libdrm2 2.4.101-1
version.libgl1-mesa-dri: libgl1-mesa-dri 20.0.4-1ubuntu1
version.libgl1-mesa-glx: libgl1-mesa-glx N/A
version.xserver-xorg-core: xserver-xorg-core 2:1.20.7-2ubuntu2
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev N/A
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:19.1.0-1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917+git20190815-1
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.16-1