@HannahDonor First, if you haven't already done so, I highly recommend that you clear the cache on your browser and then try accessing the assignment again. Many times this helps resolve a multitude of page load issues. These Canvas guide explains how to clear your cache: How do I clear my browser cache on a Mac?
How do I clear my browser cache on a PC?
You don't mention what type of assignment that this is, but I suspect it might be a discussion since you mention a "reply" option. Without knowing the specific assignment this is occurring in, it is difficult to troubleshoot. If clearing the cache doesn't resolve your issue, you may want to contact Canvas Support about the issue and be sure to include a link to the particular assignment that you are having issues with. How do I contact Canvas Support?
