Many user reported that they are getting no app icons when they updated their Mac to high Sierra recently. Their apps icons is replaced by some developer version icons with canvas.
#1. Restart your device
Restarting your device may solve problem with macOS 10.13. You can just click on apple logo on extreme top left and press shut down.
Turn your Mac or MacBook with power button on keyboard. And then try again to install the update on your system.
#2. Force Restart your Mac
Force restarting your Mac will fix the problem with updating macOS to high Sierra.
Just press down power button on right top corner of the keyboard on your Mac or iMac. Just start your Mac again to fix the problem.
#3. Reboot your Mac to safe mode
Rebooting your Mac to safe mode will surely fix the problem “An Error occurred while verifying firmware”.
To do so Re-booted your Macbook pro into safe mode , hold down shift key on startup.
Then Re-start upgrade from applications folder and it will install.
It may take a long time to install with a couple of reboots but got there in the end.
Also read your mac don’t wake up from sleep
Thus will fix the problem “High Sierra no App Icons”.