While rare, this does happen from time to time. When this occurs, go to the LexVid home page and look to see if the course is still in your Playlist marked 100% complete or on your Completed Courses & Certificates list.
If it's on your Playlist, you'll need to email customer service at firstname.lastname@example.org and we will mark that course complete and issue your certificate. You'll know this has been done when you receive your certificate in your email.
If it's on your Completed Courses list, there's nothing else for you to do. The course has been marked complete and the certificate has already been emailed to you.