Open Facebook and go to the post you want to share
Click or tap the audience/privacy setting on the post
Select Public
Save the privacy setting
If posting from a Page, make sure the Page post is published
If posting from a profile, avoid setting the post to Friends, Only Me, or Custom
Check that sharing is allowed in the post settings
Avoid using restricted groups or private group settings if you want wider sharing
For old posts, edit the audience to Public if available
Verify that the post does not contain content that Facebook limits from sharing