io.emit fails to emit to all clients

I am trying to implement a "leave game" feature in a simple socket.io game and I cannot figure out why io.emit notifies only the socket of the client leaving the game. Here is my socket.js code:

io.on("connection", sock => {

    sock.on('joinGame', name => {
       inc++
       if(name === 'guest') name = name + inc.toString()
       addToGame(inc, name) // adds player to a new Map()
       io.emit('joinedGame', name)   
    })

    sock.on('findPlayersInGame', () => {
       getAllPlayersInGame(io, threeOrMore)
     // check to see if the client is notified when a new user joins
       io.emit('newPlayerJoined', 'new player joined')
    })

    sock.on('leaveGame', name => {
       io.emit('leftGame', uniquePlayers)    
    })

On the client, I am handling the socket communication along with my state management in a MobX store. Here is my GameStore.js code:

export class GameStore {
constructor(aGame) {
    extendObservable(this, {
        players: [],
        game: aGame,
        menuVisibility: true,
        play: action((id, username) => {
            this.menuVisibility = false
            username === undefined ? this.game.setName("guest") : this.game.setName(username)

            // join game with given username
            sock.emit('joinGame', this.game.playerName)

            // after joining, if the username is 'guest' change name to unique guest name provided by server
            sock.on('joinedGame', name => {
                if(this.game.playerName === 'guest') this.game.setName(name)
                console.log(this.game.playerName + " joined the game")
            })
            // populate player list with all players in game room
            this.loadPlayers()
        }),
        quitGame: action(() => {
            //this.menuVisibility = true
            sock.emit('leaveGame', this.game.playerName)
            sock.on('leftGame', players => { // this should be logged to all clients
                console.log('updated player list', players)
                this.players = players
            })
        }),
        loadPlayers: action(() => {
            sock.emit('findPlayersInGame', this.game.playerName)
            sock.on('loadPlayers', players => {
                console.log('loading players...')
                this.players = players
            })
            sock.on('newPlayerJoined', player => {
                console.log(player)
            })
        })   
    })
  }
}

When I dispatch the quitGame action, the socket only emits to the client that is leaving the game. I need to update the player list in my store after someone leaves the game, but I cannot figure out why the other clients are not getting the message that someone left the game. io.emit seems to be working fine when a player joins a game.

via Mahmud Adam