In Control, you will often come across a blocked passage or sector that is not yet available/ How to open these types of passages? The solution is on the next page of the guide.
In most cases, you have to be patient. Many locations aren't available until you get, for example, levitation or a higher Clearance Level. Only then, you will be able to open the door or reach new rooms.
Some places are also infected with mold and entering them will lead to loss of health. In this case, you must complete Old Growth side mission to make Jesse get vaccinated and resistant to the mold's effects.
In addition, many locations also have hidden rooms, which are very difficult to reach. When you get to the secret places, the game will reward you with, e.g. an additional skill point, a few other materials, etc.