While in Vacation Mode, your nation will be unable to declare wars, fight existing wars, be declared war on, spy on other nations, be spied on, receive any sort of revenue, pay any bills, trade with other nations, or use alliance banks. There is no way to end Vacation Mode early. Vacation Mode is not intended as a tool to use to avoid wars, and it is not a "peace mode". Once you put your nation in Vacation Mode, administrators will not reverse it for you, and you must wait the length of time you chose before you will regain full access to your nation.
Mayor's post in Vacation Mode bug was marked as the answer