friends, I have iPhone7 I have problems connecting my WIFI, and at the same time same environment my iPad and Mac connect fine. I had this problem for several month, I visited Apple Store in China, and came back to reinstall OS (I'm a software engineer), I even went Apple Store in Apple campus in Cupertino (my US home is nearby there), and I was on my phone running test with the Apple support, all showed everything is fine and no wifi hardware problem.
Last week I was in Hong Kong, and close to the Apple Store in Central, so I decided to try my luck. After hearing my problem and what I have been thru. The staff there REPLACED my iPhone 7 for free. He told me they have seen similar problems with about 300 hundred customers.
So friends, talk to Apple about this, and if you have tried my steps and still doesn't work, you need to ask Apple to replace your iphone7. I wasted so much of my time, turn off the phone and restart which was the only way to get wifi to work. And even the turn ON and OFF does not always work. It wasted so much of my time.
I hope you don't waste your time.
Im disappointed by Apple Cupertino store and their support when they know about the problem they don't replace my phone. Truth is even Apple disappoints.