Oops… there was a problem during the request...... (1 reply)

Hi
Ｉhave a problem, when I set the Period time with "week" or "month" or "Date range", There will show “Oops… there was a problem during the request. Maybe the server had a temporary issue, or maybe you requested a report with too much data. Please try again. If this error occurs repeatedly please contact your Piwik administrator for assistance.” in the page.
How can I fix it?
thank you a lot.