Stupidsome question... how can I link maps in the custom campaign?

Hello everyone!
I have some problems making my campaign! I've got some maps already done and I've used the Campaign Editor in order to make a "Demo" to try it. I've loaded three maps in "General" and I've put their own Buttons and names in the "Loading screen", making the first mission Visible so you can start playing the campaign by the first mission. The problem starts when you play and finish the first mission; when you're back to the Campaign Screen, the second mission button won't appear! What must I do for making the buttons appear after passing missions?
Any help would be grateful :D

You must activate the campaign button using the triggers, and if you want the next map to begin when you finish the current you must use "set next level", also in the trigger