This document explains the meaning of the "Tag RELATE_CLASS_NBR_1 has an invalid value 0" error message and how you can resolve it.
What it means:
Course enrollment failed: Tag RELATE_CLASS_NBR_1 has an invalid value 0. Check and try again.
What to do:
Pink enrollment error message:
Remove the course from your cart and add it again.
You might still be seeing an error message from the last time your attempted to add the course to your cart or enroll. The message does not refresh/revalidate and will stay on the page until the next time you try to enroll.
You can select the checkbox next to the course and click the "Revalidate button", or simply disregard the error message, select the checkbox next to the course and then and click the "Enroll" button.
Sad Bucky when trying to swap classes:
If possible, perform the swap manually- drop one course and enroll in another.
In case that is not an option, call the Office of the Registrar at (608) 262-3811.