Why won't my iPhone 6s update?

I've been trying to update my phone with iOS 10.2.1 but it keeps saying I'm not connected to the Internet. I'm at home connected to my wifi, and it still isn't updating. My husband and I have the same phone, but his updated and mine won't. We are connected to the same wifi. I've tried to update over the span of about 5 days now and nothing is working!! Help.