Mind posting a screen shot of the room? That will really help us come up with an explanation.
@Turbo_Starr
Often times, stuff on or near a wall can cause a problem, including stairs and such. If the room to be moved has stairs near the wall, lights near the wall, or any doc items on the wall, this can be an issue.
If you are getting a "blue" outline and doorways but it won't let you drop the room into place, there's probably a bug somewhere. You probably have to contact a GM.
When it won't let you place a room due to objects in the way, the outlines stay red.
-np
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I have run into this a few times... what caused it for me was I changed the location of the door or added a second door to the room then tried to move it and it wouldn't so what I had to do was move everything out of the way of all the possible the door areas on that side in order to move the room, also you can flip rooms to conform sort of like how you flip items by clicking on them hope this helps 
It's better to save the Mystery, than surrender to the secret...
When I redesigned two of my bases, I had a similar problem.
I KNEW a door was possible where I wanted it (it's where it was before I moved it) but the editor just wouldn't let me place it.
xxxxx
xxxxxb
xxxxx
xxxxx
xxxxx
o
o = is where the door was
b = is where the editor would let me place a door iirc
I wound up increasing the size of the base (for more wiggle room) and dropping extra rooms/security corridors down to get the room in the right place, then making a new door where I wanted it to be. Place doorway worked fine.
It was a major faff but did work in the end.
Just hope you have the prestige to do something similar.*
*
As has been said, stairs and even dirt piles near the door has caused me issues before.
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We even tried placing 4 security corridors as a frame, then attempted to move the room inside. It would have no excuse on the door locaions. Still didnt work. The only other option we see at this point is removing tiems from all the walls. 
yes, that is likely what you will have to do. remove all wall items in the area you want the door to be, and also remove the wall items from the room you are attaching it too. you may also need to remove any items placed on the ground near these desired doorways. they can be replaced once the room is moved/rotated as needed. i run into this issue all the time.
there used to be an issue with moving rooms with stacked items, too, but it seems this has been fixed.
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a wise man once said...
"don't screw this up."
Recently a friend of mine was doing base edits and ran into an issue with one of his rooms. He was trying to move the room to another section of the base, to make the base 'flow' better. For some reason the room just wont move. It wont even rotate. The room was originally moved and rotate into its current location a few weeks ago. Yet this 2nd move just wont go through, even though everything lines up correctly and we even see all blue doorways.
Any ideas on how to handle this with out deleting items, or (worse case) rebuilding the room?