Don’t get panic if you face error 4002, as we are having the solution for you.
This error message occurred when your facebook access token gets expired or you have changed the password. So you need to remove your facebook account and add it again to the Facebook Poster.
This error message means that the Facebook account ID is not correct, while adding Facebook account Facebook may generate a scoped ID instead of Real Facebook account ID
Click on the edit button as shown below
Then Set your Facebook ID by finding the id upon clicking on the Find my Facebook ID and generate the id and put the numeric ID in the below box.
This will solve your Error 4002 problem.