Using openSUSE Plasma 5.9.4-1 with corresponding kwin5. ("Tumbleweed" latest and greatest, built 2017-03-21). When switching desktops within the primary panel's "desktop switcher widget", and also when switching via shortcut (keyboard or mouse switching), then "desktop switcher widget" does not show that you have moved to a different desktop. The highlighted desktop indication is "stuck", and does not move. With Plasma-5 (or kwin, I don't know where the "responsibility" lies) unable to provide different desktop back ground images per desktop, the pager becomes more critical to see "where you are" among your virtual desktops. The pager works great for moving application windows among desktops - it just doesn't update the highighted "desktop" correctly.
Looking more carefully, it *is* working. The too-subtle-for-me-to-see highlighting would be a theme issue, if we see a bunch of duplicate reports in the future.