Multiple Buildings Placement

Hello. I have a building system in place and buttons that act like the building image and etc. When I press the button, the building instantiates correctly, it can be placed correctly, everything works fine.

However when the building is placed then that's it, I cannot place the building again unless I press the button again and I know it does that because when the building is placed the prefab holder is set to null.

Here are two code snaps:

This one is used to place the building:

 public void PlaceFixture()
     {
         if (Input.GetMouseButtonDown(0))
         {
             fixtureToPlace.layer = 0;
             surface.BuildNavMesh();
             fixtureToPlace = null;
             isPlaced = true;
         }
     }
 
 private void Update()
     {
         if(isBuilding)
         {
             Time.timeScale = 0;
             visualGrid.SetActive(true);
             MoveObjectToMousePosition();
             RotateObject();
             PlaceFixture();
             
             if (Input.GetMouseButtonDown(1))
             {
                 Destroy(fixtureToPlace);
                 isPlaced = false;
                 fixtureToPlace = null;
             }
         }
     }

And this is the one used for the button:

 public void PlaceFixture()
         {
             buildingSystem.isBuilding = true;
             buildingSystem.fixtureToPlace = Instantiate(modelPrefab);
             modelPrefab.name = "Shelf";
         }

The script above is used in a prefab that gets it's information from a scriptable object database and I cannot simply simply say in the first script to just repeat that because it needs to search for that specific item in the list.

My question is what can I do/change to instantiate another building immediately after the first one is placed without clicking the button multiple times?

Thanks in advance!