Instructors may want to use Canvas' "Student View" option to open Qwickly Attendance. Unfortunately, Canvas' Student View is not compatible with Qwickly Attendance.
Qwickly Attendance uses Canvas' REST APIs to detect and authenticate the user who is opening the tool. Attendance will attempt to make sure that the user who has requested to open the tool is the same user who is currently logged into the system. When an Instructor uses "Student View", Canvas does not actually log the instructor in as a real student account, but rather creates a "Test Student" account in the course. This user account does not have any permissions to run REST APIs and get course information.
Thus, Qwickly is unable to load any information when this happens and will display a "Server Response Error".
For information on how Qwickly Attendance works for students: https://qwickly.zendesk.com/hc/en-us/articles/360049481091-Qwickly-Attendance-LTI-Student-View