Cannot lock keychain

Hello origamiship,

Thank you for reaching out to Apple Support Communities, and we'll be happy to help in any way we can. We understand you're having issues with iCloud Keychain options on your Mac. We recommend reaching out to Apple directly for assistance with resolving this issue here: Get Support

We hope this helps.

Cheers!

Has the User ever forgotten the Computer Admin Password and has had to Reset the Computer Admin Account Password vis Recovery Mode ?

If Yes, a new Set of Keychain Passwords would have been created/

Thusly, the Old Keychain may not be accessible and would dovetail into what is being experienced on this computer now.

Is the User the Owner of this device.

Owner as in, the User Account Setup on this when it was New Computer .

Apple Computers can have several User Account. Some Are Admin Accounts and can even have an Added Admin Account, Standard Accounts. Guest Account.

Only the Owner Account ( default Admin ) account would have access to the Keychain and be able to remove System Keychain Passwords