An open door is not a destination. You need to keep moving once you enter a new place because that new place is only one point on the map of your life-journey. It was never intended to be your final destination.
The same faith that allowed you to see the first open door will be there for you once again as you move through this unfamiliar territory toward the next doorway that is not yet visible.
A life of faith does not produce destinations where we are allowed to become stationary. We need to keep moving, not as a neurotic version of a life empowered by human works and the need to always have to produce something, but as someone who lives in a moment-by-moment willingness to respond to the leading of God's Spirit. The Lord is always drawing us deeper and farther into the things of the Spirit.
There is a new doorway just ahead of you that God will ask you to open. Keep moving forward and deeper in your faith and you will see the next doorway at just the right time.