iCloud must approve a new device?

Last week, my CEO had to get a replacement iphone (due to his being damaged). When the phone provider assisted with setting up his new phone, they had him use his same PIN and Password on the new phone that he used on his old phone. He is now getting AppleID popup notifications telling him to sign in with his apple ID. When he does he is being instructed that the phone needs to be approved through iCloud on another apple device he has. Any guidance on this would be greatly appreciated, because I know when I go to my ipad and go to icloud, I see my other apple devices, but see nothing that would allow to tap on to allow a device.