Hi @AndrewMeador !
Thanks for reaching back out.
While I don't believe this should be a reason, you by chance aren't enrolled in the course itself with a role that would prohibit you from concluding it, right? Is the role in your course the canvas-provided teacher role, or is it a custom teacher / ta role that you created for your instance? And, you aren't enrolled as a teacher in one section and a student in another section of that course, right?
The only other thing that could come to mind would be any course start and end dates that you have set-up at the course level, or any term dates you have set-up at the account level. Do you by chance have any of these set-up with your account / course?
When a course is concluded, it will automatically be removed from both your dashboard, and the courses slide-out tray. However, you'll still be able to access it from your 'Past Enrollments' via the 'All Courses' page. If you are interested in still moving this course out of your Dashboard / Courses list even though it isn't concluded, you can click on the Courses button via the global navigation bar > All Courses, then you'll see orange stars for all of the courses on your dashboard. If all of the stars are not filled with orange, that means all the courses are visible. You should only star off the ones that you want to see. That said, ensure this course that is supposed to be concluded, doesn't have the star filled in from the courses menu.