Active Mission sites may be removed during a server maintenance (downtime) if the mission they belong to had its objective marked as completed. As the completion often occurs as the required mission item becomes available for pickup, it is for this reason that players are advised to only accept and begin any mission they feel they can complete and pick up the mission item before the daily maintenance begins.
If a mission site has been removed while the mission objectives had not been completed, then players may be able to reset the mission site by docking and undocking from a station or leaving and reentering the system. They should then warp to the mission location to check if the site has respawned.
Any player who finds themselves in this situation and are unable to respawn the site themselves by docking then undocking, may submit a ticket to Customer Support requesting that the mission be reset. Such tickets should be submitted to the 'Agent Mission in Progress' ticket category. Any mission reset granted will fully reset the mission and return it to an offered state. Players will therefore need to contact their agent to accept the mission.