Please make sure that you check each section in the course. If there is no de-crosslist button then that section was created in that specific course and cannot be de-crosslisted. You might also check with your Canvas Admin about the permissions for cross listing/de-crosslisting.
Robbie
Hi @monica_gingeric
When you say the de-cross list button is not available, do you mean the button is grey'd out or the button does not show up at all?
I'm guessing you're following the guide: How do I de-cross-list a section in a course as an instructor?
If you can provide an edited screen shot of what you're seeing, we'll be able to give better advice on what to do next.
From the guide:
Note: If you cannot view the De-Cross-List this Section button, you no longer have an enrollment in the original course. For assistance in de-cross-listing a section, please contact your Canvas admin.
And as always, you can use the Submit a Help Ticket button from the Help menu in Global navigation to report the issue directly to Canvas.
Hope one of these solutions works,
Cheers - Shar 
Hey Sharmaine,
This was a great answer you gave! Thanks for being so helpful to your fellow community members, especially in these difficult times. Please check your direct messages for a small token of our appreciation. 
Thanks again for all that you do and keep up the good work!
Sincerely,
Canvas Community Team
Please make sure that you check each section in the course. If there is no de-crosslist button then that section was created in that specific course and cannot be de-crosslisted. You might also check with your Canvas Admin about the permissions for cross listing/de-crosslisting.
Robbie
