Try a couple of things: make sure you have Keychain sync on in iCloud and that you're logged into the same iCloud account on both iPhone and iPad. Also, in keychain, you must enable "approve with security code."
Then try a hard restart on both devices, and give it a minute. If it still does not sync, unfortunately I think that you will need to reset your home configuration. I know that is a complete pain, and I feel that pain as I have had to do this a dozen times. I have dozens of devices, and in the end I have determined that it is best to always add devices using one primary iPhone.