Unable to click on new housemate

There are two options you could have chosen to get him into the house. One takes longer to get to come up. Did you ask him to move in or to be your roommate? Move in is what you wanted. Be your roommate means he will take up a household space, but you have no control. Like dorm mates in university. You can try to split and merge the household. I hate how money works when that happens, however. Make sure one of your sims uses their phone to turn off roommate services, or afterwards more random roommates may show up.