See this forum post
On the attached screenshot you can see that showing data for time periods doesn't work. Simply choose a time period and then click on "related report: ..". No data will be shown. Additionally switching back to normal browser data doesn't show any data anymore afterwards. I had the same issue for related reports to operation systems.
On my own piwik installation I got an error/exception as posted in the forum entry. In the demo I do not get this but as mentioned before it there seems to be an error.
Keywords: related report, time period
Attachment: shows no data available for time period
thanks for the report. NOte: it works in sub-reports and fails only on dashboard.
(In ) Fixes #3683, decode URI parameters in related report JS after parsing URL.