Hi Rae Anne,
I saw something similar this week with an instructor. The instructor could not see his comments or student comments in the speedgrader, however he did see them from the gradebook view in the slide-out try for the student. The problem was that the assignment was a group assignment, but the groups in the group set assigned to the assignment had no students assigned to them. That is, the instructor created the groups, but did not place students into the groups, they were empty. As a result, Canvas did not know how and where to display the comments.
Don't know if this is the same issue, but I hope it helps!
-Greg