Hello dzungdo
Thank you for the document and screenshots.
The Extra Credit (or setting 0 points for Assignments) must come along with at least 1 assignments having points > 0 in the same category.
So your last case is indeed what it is: having all 4 assignments set to 0 points / E/C, the final grade can't be calculated correctly due to division by zero.
I believe RosarioSIS and the Progress Report behaves correctly in this case, although there is no specific error to alert the user.
Would an error / warning message on the Assignments screen be more explicit to warn about this case?
This could be like:
Warning: Every Assignment in category "XXX" have 0 Points (Extra Credit). Enter Points for at least one Assignment so the Final Grade can be calculated correctly.