Dock icons missing

Found a solution that worked for me perfectly!!

Simple:

Step 1: remove the wrong icon from the dock

Step 2: with Finder, go to the Application folder

Step 3: Drag and Drop the application to an empty desktop. Throw it there. While you drag it will look wrong but as soon as you drop it, it will turn back to normal

Step 4: Drag and drop the correct icon from the desktop to the dock. It will look back as normal

Step 5: Send to the Trash the icon that in the desktop

I have the same issue starting from TODAY when I download the recent update of Security in Sierra. I don't know if it has anything to do with the update. Did you find a solution in the meanwhile?

I don't know what causes the issue, but have you tried removing one of the general app icons, open Finder and drag the app back to the Dock from /Applications? Then, monitor to see if the app icon sticks?

Try doing a Dock restart using the following Terminal command:

killall Dock

Log out/in and test. If that doesn’t work, you need to look in your user Library/Applications Support/Dock for the .db. Use the Finder “Go To Folder” command. Enter ~/Library/Applications Support/Dock. Move the .db to your desktop.

Then try a dock reset.

Applications/Utilities/Terminal enter the command

killall Dock

Log out/in test. If it works okay, delete the .db from the desktop.

If the Dock is the same, return the .db to where you got them from, overwriting the newer ones.

If you prefer to make your user library permanently visible, go to Finder and select your user/home folder. With that Finder window as the front window, either select Finder/View/Show View options or go command - J. When the View options opens, check ’Show Library Folder’. That should make your user library folder visible in your user/home folder. Learned from leonie.

Have you tried deleting the com.apple.dock.plist from /Library/Preferences; then restart?

Last thing I can think of is to add a new account and check the Dock out for that user. If it's working, then it may have something to do with your user account. What? I wouldn't know.