Here is the bug that you might be encountering. If you are using the Auto Save or Exit Save games, you will not get any new campaign missions. You have to use your own uniquely named save files in order to continue the campaigns. I hope you have a saved file for your campaign which isn't too old.
If the game has stopped feeding you campaign missions, there is no way to get them to start. Going to the right hex does not work, I'm sorry to report.
Good luck.