I have Enable Display Cumulative Marks set to Yes and using the Percentage Attainment Scale. However, nothing is showing up in the Cumulative column, What extra step(s) do I need to take. I know I’ve seen a value in this column in past installations.
Can you check that your school grade scale in System Settings is also set to Percentage? You’ve mentioned the grade scale, but it may only be applied to the columns themselves.
That is correct that only one default grade scale can be specified for all classes. However, this is just the default, and any time a grade scale is used, such as in the Markbook, this can be manually overridden.