Missing Dock in Ubuntu 20.04 after sudo apt upgrade and restart

I did sudo apt upgrade and restarted Ubuntu 20.04 system. However, after login the Dock is missing from the desktop environment. The Dock does appear on the left edge of the monitor when I press the Super button to enter the Activities screen.

I have tried solutions 1 and also doing

$ sudo apt install gnome-shell-extension-ubuntu-dock
$ sudo dpkg-reconfigure gnome-shell-extension-ubuntu-dock

Each time reboot to check the appearance of the dock. Still missing.

noticed something strange in Settings --> Appearance --> Dock. Icon size is 0 and can't be changed and Show on is blank. Position on screen was initially blank. I could selected any of the options but Dock still does not appear. See image

Quite sometime ago, I had installed Dash-to-Dock and uninstalled it. Dock still appears and worked well for weeks until this upgrade. According to apt log, the affected packages were:

Upgrade: brave-browser:amd64 (1.27.111, 1.28.106), libegl1-mesa-dev:amd64 (21.0.3-0ubuntu0.2~20.04.1, 21.0.3-0ubuntu0.3~20.04.1), libegl-mesa0:amd64 (21.0.3-0ubuntu0.2~20.04.1, 21.0.3-0ubuntu0.3~20.04.1), update-notifier-common:amd64 (3.192.30.8, 3.192.30.9), libwbclient0:amd64 (2:4.11.6+dfsg-0ubuntu1.9, 2:4.11.6+dfsg-0ubuntu1.10), grub-common:amd64 (2.04-1ubuntu26.12, 2.04-1ubuntu26.13), libglapi-mesa:amd64 (21.0.3-0ubuntu0.2~20.04.1, 21.0.3-0ubuntu0.3~20.04.1), libglapi-mesa:i386 (21.0.3-0ubuntu0.2~20.04.1, 21.0.3-0ubuntu0.3~20.04.1), libxatracker2:amd64 (21.0.3-0ubuntu0.2~20.04.1, 21.0.3-0ubuntu0.3~20.04.1), grub2-common:amd64 (2.04-1ubuntu26.12, 2.04-1ubuntu26.13), grub-pc:amd64 (2.04-1ubuntu26.12, 2.04-1ubuntu26.13), libgbm1:amd64 (21.0.3-0ubuntu0.2~20.04.1, 21.0.3-0ubuntu0.3~20.04.1), samba-libs:amd64 (2:4.11.6+dfsg-0ubuntu1.9, 2:4.11.6+dfsg-0ubuntu1.10), grub-pc-bin:amd64 (2.04-1ubuntu26.12, 2.04-1ubuntu26.13), firefox-locale-en:amd64 (91.0+build2-0ubuntu0.20.04.1, 91.0.1+build1-0ubuntu0.20.04.1), libgles2-mesa-dev:amd64 (21.0.3-0ubuntu0.2~20.04.1, 21.0.3-0ubuntu0.3~20.04.1), distro-info-data:amd64 (0.43ubuntu1.5, 0.43ubuntu1.6), libgl1-mesa-dev:amd64 (21.0.3-0ubuntu0.2~20.04.1, 21.0.3-0ubuntu0.3~20.04.1), libgl1-mesa-dri:i386 (21.0.3-0ubuntu0.2~20.04.1, 21.0.3-0ubuntu0.3~20.04.1), libgl1-mesa-dri:amd64 (21.0.3-0ubuntu0.2~20.04.1, 21.0.3-0ubuntu0.3~20.04.1), libsmbclient:amd64 (2:4.11.6+dfsg-0ubuntu1.9, 2:4.11.6+dfsg-0ubuntu1.10), shim-signed:amd64 (1.40.6+15.4-0ubuntu7, 1.40.7+15.4-0ubuntu9), libgl1-mesa-glx:i386 (21.0.3-0ubuntu0.2~20.04.1, 21.0.3-0ubuntu0.3~20.04.1), firefox:amd64 (91.0+build2-0ubuntu0.20.04.1, 91.0.1+build1-0ubuntu0.20.04.1), mesa-vdpau-drivers:amd64 (21.0.3-0ubuntu0.2~20.04.1, 21.0.3-0ubuntu0.3~20.04.1), mesa-vulkan-drivers:i386 (21.0.3-0ubuntu0.2~20.04.1, 21.0.3-0ubuntu0.3~20.04.1), mesa-vulkan-drivers:amd64 (21.0.3-0ubuntu0.2~20.04.1, 21.0.3-0ubuntu0.3~20.04.1), update-notifier:amd64 (3.192.30.8, 3.192.30.9), mesa-va-drivers:amd64 (21.0.3-0ubuntu0.2~20.04.1, 21.0.3-0ubuntu0.3~20.04.1), libglx-mesa0:amd64 (21.0.3-0ubuntu0.2~20.04.1, 21.0.3-0ubuntu0.3~20.04.1), libglx-mesa0:i386 (21.0.3-0ubuntu0.2~20.04.1, 21.0.3-0ubuntu0.3~20.04.1)
End-Date: 2021-08-20  06:44:43

How do I get the Dock to reappear?

Update

@vanadium I can't enable Ubuntu Docks from Extension or Tweaks. See below. Can't do your step 4.