Hello Grandblue,
I see that you're having an issue with iCloud Keychain after updating the software on your device. I know that it's important to have this feature working properly, and I'd be glad to work together with you on this issue.
Take a look at the article below that provides some troubleshooting steps that can help with what you've been experiencing.
Get help with iCloud Keychain
If you go through the steps in this article for the issues that you've been dealing with, respond back with some more details. If you sign out and back in to iCloud, does the issue remain? Do you have other iOS devices that you use iCloud Keychain with? If so, are you having the same issue on those devices?
I look forward to hearing back from you.
Have a great day!