I don't know is your being in the campaign affects this suggestion, I only know about the sandbox game.   In sandbox games, when turns stop advancing, it's usually because some unit has its path blocks and so is unable to complete its move.  So look for units on auto-explore, or units where you set the destination at more than 1 turn's distance.

Some report something about animations not playing out and zooming all the way out allows then to play out, fixing this.  I can't say if this is true, but it's worth a shot.

I seem to recall there being a third option, but can't remember it atm.  Hopefully if there is, someone will pipe up.