Didn't see this specific issue in the forums.
I turned on 2-factor authentication. After that, 1P X displayed a message that the password "...couldn't be saved to Generator History."
I had already logged into my account in the same browser session (after it prompted me to when unlocking 1P X).
Restarting the browser and disabling/re-enabling the extension did not change the behavior.
Disabling 2FA on the account and restarting the browser removed that message about saving to generator history and did save the generated password.
1Password Version: Not Provided
Extension Version: 1.15.1
OS Version: Mac OS 10.12.6
Sync Type: Not Provided