iOS 10 stuck on approve this iPhone from another one of your devices

I have a MacBook Pro with El Capitan 10.11.6 signed in to iCloud. I also have an iPhone 6s Plus which is also signed in to iCloud. After upgrading my iPhone to iOS 10 I have follow-ups showing notifications and also frequently appearing push notifications about "approve your device".

I push it, then enter my passcode to iPhone and see this:

Approve This iPhone Go to one of your devices signed in to iCloud to approve this iPhone.

Waiting for approval (spinning wheel)

Sooo... I do not have any popup or window or anything else on my MacBook to approve iPhone. How can I do this?

This is almost certainly a keychain issue. Try these steps:

1. Turn off iCloud Keychain on both the MacBook and iPhone.
2. From your iPhone, go to Keychain and tap Approve with Security Code.
3. When prompted for the 4-digit iCloud Security code tap Forgot Code.
4. Follow the prompts to reset the code.
5. Now this device should have iCloud Keychain enabled and working.
6. Now from your MacBook, enable iCloud Keychain.
7. You should get a notification on the iPhone about this. Enter your iCloud password in the prompt.
8. iCloud Keychain should now be enabled.

Hopefully this gets rid of the Approve your device notifications! Let me know how you go.

[EDIT] ***Make sure you have a passcode setup on your iCloud Keychain on your computer. If you don't set one up and then try approving your phone again. That is what made mine work. Hope this helps!