You are one step away from rebooting the system!
On the other side of this wall you will find the Plaza del Ocho de Marzo, a plant will give you the key to restart the system, you will find a red arrow that will indicate the location of the plant.
Open envelope number 4
Enter the password to reboot the system:
HINT
Search among the plants in the square, one of them has the key to finishing the mission.