Hi there, @IrmaLopez1 ...
I'm not sure if you realized this or not, but you've posted your question to the global Canvas Community website. Most of us here in the Community do not have access to your school's Canvas environment or any of your Canvas courses. So, it would be a bit difficult to help troubleshoot why you are having trouble posting to that discussion topic in your course. Have you tried reaching out to your instructor directly? This is what I'd recommend. You can click on the "Help" icon on the left-hand global navigation menu, and then select "Ask Your Instructor a Question". More information can be found at: How do I get help with Canvas?
I hope this will be of some help to you. Sing out if you have any questions about this...thanks!