Hello,

Royals I'm afraid are notoriously fussy feeders and do indeed go off their food for long periods. Nearly a year is past the serious point though and the first thing to do is take her to a vet that knows reptiles. There are lots of things that might be wrong so it's pointless at this stage to discuss them all here, let the vet take a good look first. If the vet can't find anything wrong, and it sounds like you've looked at all the obvious things, temp, humidity etc. Mites? Force feeding isn't nice and you must get the food item far enough down to reduce the chance of regurgitiation. Force feeding can also inflict injury so tube feeding is preferred. One thing I would suggest is to catch a wild rodent in the usual mouse / rat trap and see if you get a positive reaction. Obviously, under the circumstances you may need friends and family to help out with this!! The natural rodent scent frequently has a very positive response! The last resorts are twofold - and the first is very unpleasant for you. A tube is inserted into the snakes mouth and down towards the gullet, and then the liquidized mouse / rat is poured down. Not for the squeamish - and an extreme measure to be used only in a life or death situation. The last measure is to feed a live mouse / rat. This is illegal in England except through the instruction of a vet, but - He may not allow it at all, it's his decision.
After saying all that, I am of course assuming the snake is removed from it's normal enclosure and put into an empty feeding enclosure?
If it were my animal - the most obvious is to go to the vet and get an examination done, including a fecal exam.
Hope this helps, and I wish you all very best!