To find out your username or user id, go to your google profile page and then look at the URL!
Read more here!
Error occured, Username 'HTTP Error 404: Not Found' was not found; you have to use user ID instead of username.
Google username or ID: (e.g. mehrankh68 or 117037020608410847353)
It may take a bit longer for users with more than ~300 posts, be patient!