When you get a keychain prompt, tyically you have recently changed your PW, and it is asking for your old (previous) PW.
Enter it and usually that will update the keychain and you are done. There may be more than one prompt.
If that doesn't work...
you can do it manually.
It that doesn't work...you can reset it,
which kills everything saved in KC and makes a new one:
- Open Keychain Access, which is in the Utilities folder within the Applications folder.
- From the Keychain Access menu, choose Preferences.
- Click General, then click Reset My Default Keychain.
- Authenticate with your account login password.
- Quit Keychain Access.
- Restart your computer.