cat at shelter will not use litter box

I work at a cat shelter and we have one cat there since she was a kitten and she will not and has never used the litter box!!! We have tried that cat attract stuff that guarantees the cat will use the box and she still wont go. Im thinking she just doesnt want to share because we have multiple cats and litter boxes in each room. This is going to cause her not to get adopted and its a shame bacause she is such a sweetie! Does any one have any ideas? Im sick of cleaning up the floor! Also she has been to the vet and they see no medical reason.

Have you tried a different type of litter? Either one that's unscented (if you're using scented), or one that may be easier on her paws, or even having a 'private' box for her in a separate room (I know it's a shelter)?

You do say yourself her problem may be the other cats... It happens cats shows dominance by refusing the "underdog" to use the litter...

A way to train is confined in a small room. Laying place in one corner, food in next corner, water in third corner, litter in fourth corner. some classical cat sand, or even common sand. Never any fancy scented stuffs.
She will typically willy-nilly use the litter...

If you dont have small extra room try to use a well cleaned dog crate. Big enough.

thanks, We have 1 small room with 3 cats in it but no empty rooms. Ill try to talk them into putting her into a cage and see if she uses it there. If she does, we may be able to take her to Petsmart where we have an adoption center, and get her adopted. If we cant find out if she will use the litter, they wont adopt her out. wish her luck!