I keep trying to page my instructor using the pager inside D2L, but I never receive a response.

Many instructors do not use the pager, and some have the pager highlight and sound disabled. If you try paging and do not hear from your instructor soon, this is probably the case with your instructor. Try contacting your instructor using a different method, such as email. Many instructors give instructions for how students should contact them at the beginning of the course or in their syllabus.