Keychain password doesn't always work

Hi,

I often use Keychain to suggest a password for a site and a get the "This password will be saved in your iCloud keychain . . . " message. However, when I return to login into the site the password will not be entered and all I get is another suggested password. The previous password is lost/forgotten.

One site this has happened with is my Social Security Administration account, but it isn't the only one Are there certain types sites that the Keychain password will not work for?

Thanks!