I see that no one has responded to your question. If you're able to provide some additional information about the issue you're encountering, then perhaps someone will be able to assist you. Some questions that might be helpful to answer are:
1. Are you signing in to iCloud on your MacBook Pro from System Preferences, or a web browser?
2. Do you receive an error message?
3. If you do not receive an error message, could you tell us more about what happens when you try to sign in?