You might want to try the following from this link
If you can't sync iCloud Keychain with other devices.
Make sure that your device is on a Wi-Fi or cellular network. If the connection appears strong, try these steps:
Turn off iCloud Keychain on all devices.
Turn on iCloud Keychain on the device that has the most up-to-date keychain items.
Turn on iCloud Keychain on your other devices. They will be updated with your new iCloud Keychain.