Qt application error

[BlinCT .]

Hello.
Anyone can tell me, why would can this error when I try starting
application?

QML debugging is enabled. Only use this in a safe environment.
This application failed to start because it could not find or load the Qt
platform plugin "xcb"
in "".

Available platform plugins are: eglfs, linuxfb, minimal, minimalegl,
offscreen, xcb.

Reinstalling the application may fix this problem.
Emergency stop (memory dump is made)
----------------------------------------------------------------------------------
If necessary, I use Qt 5.7.0, and use dynamic libraries qt

It's my snapcraft.yaml

name: timerproject
version: "1.0"
summary: timer
description: |
    Application for time-management
confinement: strict
architectures: [amd64]

apps:
    timerproject:
        command: desktop-launch ProjectTimer
        plugs: ['home', 'unity7', 'x11', 'opengl']

parts:
    timerproject:
        plugin: copy
        files:
            bin/ProjectTimer : usr/bin/ProjectTimer
            setup/gui/icon.png : usr/share/icons/timer.ico

    integration:
        plugin: nil
        stage-packages:
            - libc-bin
            - libxkbcommon0
            - ttf-ubuntu-font-family
            - dmz-cursor-theme
            - light-themes
            - shared-mime-info
            - libqt5gui5
            - libgdk-pixbuf2.0-0
            - libqt5svg5
            - appmenu-qt5
        after: [desktop/qt5]
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