Admin Reports Broken

The admin reports used to work fine, and now I can’t generate a report for a longer date range than about a month. I think there must be some upper end on how many transactions it can handle. I believe everything is updated. I’ve cleared the site cache a few times and tried various workarounds but the report just comes up blank (no commisisons) if I go for more than a few weeks.

The page I need help with: [log in to see the link]