We are using piwik for around a year to track around 700 of very light-traffic sites. Everything was working fine untill recently, when "All Websites" (index.php?module=MultiSites&action=index&idSite=9&period=day&date=yesterday) started to return a blank page. All other pages work fine, tracking also works.
No errors found in piwik nor apache nor mysql logs.
No errors found in piwik nor apache nor mysql logs.