My cat is peeing all over the house.HELP!?!?

I have 2 cats but my problem is with one. We have to litter boxes in open areas. They go poo in the boxes but rarely pee. I put i diffuser in one area and I think he stopped but know I think he found a new spot. I clean the litter boxes (I don't wash them often but I empty and refill and scoop up. Is that okk?) I pick the cat up and place it in the litter box but it just runs off. Sometimes I even rub it;s paws in the litter. I give it a treat if it goes pee. Please help.