This is going to sound kind of silly but, put another litter box in your house for your cats to find. Recently I had put a litter box in the guest room because we were going to be having some work done in the room the cats have been staying in. I can’t tell you the how joyful they were when they discovered the new litterbox, lol. It was like that episode of Malcolm in the Middle when Louis and Hal discovered their hall closet was actually an extra bathroom, lol.