MacOS – Mac Show All Windows for an app in dock Sierra

It appears that Single Application Mode has been activated. Open /Applications/Terminal and copy the following command:

   defaults write com.apple.dock single-app -bool false killall Dock

To reverse this, replace false with true.

Alternate GUI Way

You can also Option + Click the app icon in the dock to reverse the behavior.

You can assign a keyboard shortcut to the "Bring All to Front" menu item from System Preferences:

The activate AppleScript command also raises all windows:

activate application (path to frontmost application as text)

If you are assigning keyboard shortcuts to opening applications, you can use scripts like this:

tell application "TextEdit"
    reopen
    activate
end tell

reopen opens a new default window if there are no open "default" windows, like a text editor window in TextEdit. If all default windows are minimized, reopen unminimizes one of them.

It is also possible to use AppleScript to click the "Bring All to Front" menu item:

tell application "System Events" to tell (process 1 where frontmost is true)
    click menu item "Bring All to Front" of menu 1 of menu bar item "Window" of menu bar 1
end tell