Mine seems fine--the only time I've seen something like what you describe, I went back to the main kdp page and logged back in. It worked fine after that. Maybe a time-out issue?
It may have been something like that -- it's working normally now after I logged out & back in.
I suspect they're experimenting with some user interface changes, and somehow I got a glimpse of a format that isn't quite ready for prime time. There was a way to filter the current month report & to select all countries to report at once -- but the link never returned a report, and even the default report never displayed. Maybe we'll see some new reporting options soon.