Hello I have tested with your config and it is starting within 5 minutes. I did notice you have both: "Maximum time between events(minutes):": 5, and "Minimum time between events(minutes):": 5, set to a value of 5. I thought this maybe could cause a problem but it still worked as expected. Typically I do keep this to a range though such as 5-10.
Can you confirm that you are not waiting close to the military tunnel when waiting for the event to start? This setting will prevent it starting if so "Skip event if players are already at the Military Tunnel Plant?": true,