No actions can be taken Multiplayer
On multiple occasions, I have been playing multiplayer seafarers, and in the middle of my turn no actions can be taken. If I press the trade button, all the resources are greyed out. If I press the "end turn" button, the circular arrow goes away, but nothing happens. If I press any other button, the circular arrow comes back. While this is happening, the whole time, a yellow pattern is circling the outline of the button.
Have you tried typing "/reload" into the chat window? If things are stuck that will sometimes unstick them.
Another option, though riskier, is to exit the app, reopen it and try to rejoin the game. If you can get back in quickly enough (within a couple minutes) it can get things moving again.