It looks like you haven't enabled reduced scoring for that set. Visit the Sets Manager and edit that set. Check that all dates are set and that reduced scoring is enabled for that set. Then there will be clear messages about when students can earn full credit, and when reduced, and by how much.
Depending on your global defaults and any set definition files you import, a set may or may not have reduced scoring enabled when it is created/imported.
Thanks for the quick reply. Reduced scoring is actually enabled. This screenshot is from the Assignments (ProblemSets) screen. I do see what you are saying in the individual ProblemSet screen. Could this be an implementation oversight that was not extended to the ProblemSets page?
I think that Alex's assessment is correct. Reduced scoring needs to be enabled both for the course and the set. Check both closely.
Here is a screenshot of the settings with the pertinent settings circled:
Here is a screenshot of what you should see if a reduced scoring set is not yet due:
and here is a screenshot of what you should see for a reduced scoring set that is in the reduced scoring period:
Those are both taken with the current version of webwork (2.20) on the problem sets page that students see.
It's admittedly confusing that you configure this at both the course level and the assignment level. Originally the thinking was that you need to be able to enable/disable it at the course level because if you are not using it at all, then all the date settings for reduced scoring are just clutter. And then you can enable/disable it on individual sets since it's reasonable that even if you use this feature, you might not use it on all sets.
However I do note that you can effectively not use it on a set by having the reduced scoring date match the close date. So it's at least worth considering that in a future version of WeBWorK, maybe (maybe) we could remove the assignment-level switch here.