I just gotta a new sofa bed today. And about 10 minutes ago I was trying to get it into my room. It just so happens that it won't go through my door way. Ok well it would fit through my doorway but it wont turn into my bedroom from the hallway because i have a small hallway.
Take the screen out of your window and put it in that way. We had to do that once. Of course, if you have a tiny window that won't work. Try taking your door off of the entrance, the extra 1/2 to 1 inch might make a difference.
i hope you're ready for this. you will need some help because you are going to have to stand it on end and probably have to turn it as you take it through the door. this means you may have to take the door off the hinges and maybe even the legs off. good luck.
Other places I've lived I've had to remove sofa legs, remove a window, or go round the back of the house and in through patio doors. But where I live now there was one ginormous sofa that wouldn't fit in here whatever we did, so it couldn't be kept. I wish you luck, because it's horrible when that happens, and I really feel for you as it's a brand new purchase.
Some of the suggestions you already have are pretty good, especially the upright attempt. But measure carefully first, the only suggestion I can add is to remove the legs. I do upholstery, the legs should be attached to the frame with screws, so check and see, then carefully remove (make sure you put all the screws into a baggie or other container so they don't disappear. Removing the legs should make the profile of the sofa narrower, so if you can slip it in upright, that will give you a few less inches in width, then when its in the room, all you have to do is re-attach the legs. Hope this helps.
Measure the height of the door, it should longer than the width of your sofa bed. Put the sofa bed straight up, that is the legs are not sit on the floor, the width is now the height, if you have sliding pads put it under . Slide the back support portion in first, then turn the seat with the legs at an angle and push into the room. Ask someone to help you too. Don't use too much force, otherwise you will do damage on the wall or the sofa bed.