You have done every single step for Facebook instant articles configuration, and now you “are stuck in missing logo issue, then no need to worry about that i am gonna help you in solving that issue.
Go to your Facebook page and click on publishing Tools, go to instant articles option. And there you will be seeing your issue “Logo Error”. No problem , Now scroll down and go to style option. In style option, if you already created any new style, “delete that style”.
Then go to default style option, there upload your logo and Hit save option and close.
Now refresh your page and you will no longer see that issue.