Dock doesn’t appear in my Macbook Pro 2015
Resetting the Preferences list

Dock disappearing?
Follow the following steps, the could be problem with a corrupted file or other non-settings based issue.
The first thing to do is check if there are any system updates available that you can install. 
This is easy to do: click on the Apple icon in the top-left corner, select App Store, and when it opens click on the Updates tab.
Should this be empty then it might be worth deleting the preferences file instead. This will reset your Dock back to the way it was when you first got your Mac, so any app shortcuts you've since placed there will need to be added again afterwards.
Open Finder, then hold down the Option key and click on the Go option in the Menu Bar at the top of the screen. This shows a few options that are usually hidden, one of which is Library. Click this and then select the Preferences folder.

Scroll down until you find a file named com.apple.dock.plist. You'll need to delete this file (either by using the Backspace key or dragging it to the Trash).
Now reboot your machine and macOS will create a new default preferences list which should hopefully clear the problem.

If you're still getting issues then contact Apple customer support.