You can edit the map and make sure the portal is not blocking it, you can figure it out here:
I had to change the second image as tinypic had changed the original image to, well... a goblin... So if you're wondering why it looks different from the rest, that is why.
For those with this problem.....
(http://i42BannedImageSite/4t9a4z.png)
And that dont know how to fix it, well you came to the right place. I'll be telling you how to make your portal reachable.
(http://i.imgur.com/TeuzKQP.png)
Ok firstly open Map Maker and load your map. I'm sure you want a particular spot for your portal, so go there. Go where you want your portal to be. Now place an object, any object maybe a rock like me. Place that rock where you want your portal to be.
Go to the "Controls" tab now and look at the X,Y,Z coordinates for the rock, make sure you have the rock selected.
Remember those coordinates in the red circle blob thing.
(http://i41BannedImageSite/21ovr07.png)
Those coordinates need to be typed in here. The rocks X coordinate needs to be typed into the X box. The Y coordinate needs to be in the Y box. The Z coordinate needs to go in the Z box.
Just something you should know but the coordinates will not always fit. So just type in as much as can fit into the box. Its ok if you're missing one number.
This box needs to be checked. It's important, very important. If the box isn't checked there is no portal.
When you have typed in the coordinates click the button "Test" and see if the portals where you want it. The portal will never be exactly where you want it but very near. So its always good to test it. If it needs to come forwards move the rock forwards and type the new coordinates in. If its too far left move the rock into the right and copy the new coordinates.
(http://i43BannedImageSite/a1tgdg.png)
Now what if the portals faced at the wrong angle? What if its facing upwards too much and not straight ahead. Well face your camera in the direction or angle where you want your portal to be facing. Well what we are doing is changing the Yaw.
See that long box at the bottom of your screen? See that "Yaw:"? Well still facing at the angle/direction with our camera, without moving we need to copy that coordinate.
We will type that coordinate in this box underneath the X,Y,Z coordinates.
Anyway let's click the "Test" button. Is your portal facing the right angle and is in the spot you wanted? It is?! Well congratulations because your portal is now reachable.
(http://i42BannedImageSite/k4jqcw.png)
If you have any questions or comments feel free to post them up.
Thanks for reading.