If you receive enrollment instructions for a particular course,
you'll need to follow the instructions carefully. Don't rush
through this process. In particular, you have to locate the
right course (and the right batch number, if
relevant) and enter the enrollment key exactly
as given in the instructions. It's a good idea to copy the key
from the instructions and paste it in the box where you have to
enter it.
After entering the enrollment key, you can "unhide" it to see if
it matches the key given to you. Make sure there are no extra
spaces or other inessential characters.
If you can't join your course AND you're absolutely sure that you
have tried enrolling in the right course with the right
enrollment key, you may email the course facilitator to seek
help. Please mention in your email the full name of the course
you tried to join and the enrollment key you used.