Cats, to put it mildly, have a difficult time with change. Being the particular souls that they are, they’re put off by new textures, new food and even new kitty litter for their box. But there comes a time in which you all have to get used to a new brand. So how to go about it? There are two options.

Make it feel like it was their decision.
Cats are nothing if not independent. Try to get them to do something and they’ll balk. But let them think they decided, and it’s smooth sailing. So instead of just changing the litter in their box, try putting out a second litter box with the new litter nearby. This method can take some time and patience, but if you need a more immediate fix, there’s method two.

Go so slooooooowly they don’t even notice.
A little new litter here. A little new litter there. For this approach, just gradually add the new litter to the old every day over a three to five day period. Or, you can try putting a layer of the new litter in the box with a layer of your current brand of litter over it. Either way, your cat will smell the old litter mixing with the new as she moves around the box and start to gradually get used to it. Eventually, they’ll feel like new litter has been there all along.

If you must, admit defeat.
There are some cat battles you just can’t win. If they absolutely refuse to use a particular brand, it’s on to the next. And if all this change has your cat acting out by going out of the box, go easy on them. Never punish for accidents, just take them right to the litter box. It may take a while, but sooner or later you’ll find a litter that makes you both happy.