First, make sure the channel you're publishing on is the same channel you're subscribing to. (Ably channel names are case-sensitive -- sports is a different channel to Sports).

Second, make sure you're using the same app everywhere (make sure you're not, say, publishing with an api key from your Sandbox app, but subscribing with an api key from your Production app)

Thirdly, you need to find out whether the problem is on the publishing or the subscribing side. Open the dev console, attach to the channel that you're publishing on, and try a publish. Do you see the message appear there (but still not on your subscribing device)? If yes, the problem's on the subscribing side. If no, the problem's on the publishing side.

Debugging publish problems

When you call channel#publish, you can pass a callback (or equivalent - select the language you're using from the language bar), which if the publish failed will tell you why.

Debugging subscribe problems

- Check the connection state, make sure you're connected to Ably

- Check the channel state, make sure you're attached to the channel

- Make sure you've added a subscribe listener. If you added a listener for a specific event name, make sure you're publishing with the exact same event name