The Button "Refresh" has a Dynamic Action attached which triggers a Refresh on "Customers".
When clicking the Button you can see that the Report is not refreshed.
Now switch on DEBUG and open the Javascript Console of your browser. There you'll see a log message when the Button is clicked.
That log message also lets you investigate the "Affected Elements" object, which indicates that the wrong Region is used as Refresh Target.
This happened, because the Report Region is nested in a Static Content Region and the wrong Region has been specified in the Dynamic Action.