When we rehomed our 7 yr old neutered male - Oscar, he also started spraying about a month after he arrived. We thought it strange that it took a month for it to start. He was spraying on both sides of huge floor to ceiling glass doors we had. We realised he felt these doors were a weakness in his territory boundaries so he was spraying either side. We cleaned the areas very well with enzymatic cleaner which is vital to totally get rid of the smell and then sprayed the areas with spray feliway. We also put little bowls of food either side so that these areas were associated with happy hormones and yummy food. I also put a scratching post there too and used jackson galaxy product called Safe Space in his drinking water. I think the spraying is just him being territorially insecure which is not surprising if he is new to your family. Another thing to consider is has another cat been around the house outside? Is the sofa near a big window/door which he could possibly see as a weakness in his territory. Oscar did stop spraying when he felt more secure. The last time he sprayed was ages ago when we had a carpenter doing some work. Our carpenter Eddie always brings his Pointers who stay in the van but obviously the wood smells of dog! Oscar was not having that so he sprayed on the newly installed fitted wardrobes
I have never told my husband!!!!!!