Private goals work differently than normal goals. There are some simple rules for this:

• Only the owner and contributors can work with private goals. This means that only they can perform operations on them like adding an update or adding/removing supporting documents, links etc.
• Only the owner can change who the owner is.
• Only the owner can make the goal private or change that status in the future.
• Private goals won't show up in a search if you are not the owner or a contributor to them.
• Followers who followed the goal before it was made private will no longer get notifications unless they are made to be a contributor.