cat stopped using box!

my 6mo male cat stopped using the litter box. The only other pet is female sister cat. He uses select places and ignores that "stop spray". Tried changing litter, changing location, neutering, worm treatment, with litter dome without litter dome, shredded paper, multiple boxes, rubbing nose in wet spots, locking in bathroom with box, sticky tape on surfaces he wants to go on, etc.
He will go in box when locked in bathroom, but refuses when let out into house. Any one have any suggestions?!?!

Is he neutered? Male cats can be subject to urinary tract infections that can make them avoid the litterbox.

How many litterboxes do you have? You should have at least 2. Is the sister spayed? If not, that can cause the problem as well.

When cats start peeing outside the box there is always a reason - we just have find out what it is.


DO NOT RUB HIS NOSE IN HIS PEE!!!!! THIS IS VERY VERY CRUEL AND IS MAKING THE PROBLEM WORSE!!!!!!