Grade Discrepancy

This school year I've been using the Google Classroom mark book. For my class I have four categories, each one of them counting as 25% of the final grade. Each assignment in a given category is weighted according to the number of points. The Google Classroom mark book correctly calculates the final grade. I am trialing the GradeBook for Google Sheets, but after importing the same classroom into the gradebook, and setting up the categories, total points etc. the final grade is way lower than it should be. Why?

I've already noticed that there is a big gap between the grades on Google Classroom and those on Gradebook but I'm also noticing that the first student in the class is repeated so I'm wondering if that might be why?

I get this error one one of my sheets. What does it mean? I cannot send email reports from that sheet anymore.