When you use Google Classroom and you are not able to access and assignment this may be due to three different situations:
1- You are not logged in with your correct google account on EDpuzzle. To make sure you are logging in with the correct account, could you first visit https://accounts.google.com/login re-enter Google password for your account, then log out in EDpuzzle (https://edpuzzle.com/logout) and log back in by selecting the log-in button select the student option and then click the red Google button? Make sure you log in using the same email address that you use for Google Classroom.
2- You are trying to access the wrong assignment or the assignment from another class. Keep in mind that, in EDpuzzle, assignments have a different link on each class. This means that, if a teacher has assigned the same video to multiple classes, you will need to get the correct link for your class.
3- You have joined the course in Google Classroom after your teacher created the class on EDpuzzle. This means that you have not been imported to an EDpuzzle class. Could you ask your teacher to import you? He/She just need to click on the "Import new students" button in "My Classes" again.