I can access all of my course materials on the app on my phone, but when I try using my laptop the course will not show up.
My guess is that when you access Canvas on a computer the view is defaulting to the "To-Do List" view. In this view instead of showing links to your courses the content is displayed based on assignment due dates and the like. If your instructors have not put due dates on things, don't have assignments, or there is just nothing coming up in the next few days you might not see much.
Try clicking the Courses button on the left side of Canvas and see if your courses are listed. This is one way to access your courses directly, even if they are not showing in your Dashboard. Better yet, you can change your default view in the web interface to Card View which will make it look more similar to what you are seeing in the mobile app. To change the view click the Kabob icon (3 dots) in the upper right corner of Canvas and select Card View.
I'm also including a few links below which might help.
No, it shows up on the phone but not on the computer. It literally says I have no courses. On my phone, all my courses show up as N/A but I can still see the syllabus and everything else required for the class. I want to see what I see on my phone on my computer. It doesn't even show my picture or calendar as it shows on my phone. My phone has more information while, on the computer, information is lacking.