Not able to reproduce that on our demo: https://demo.piwik.org/index.php?module=Widgetize&action=iframe&forceView=1&viewDataTable=graphEvolution&widget=1&moduleToWidgetize=VisitsSummary&actionToWidgetize=getEvolutionGraph&idSite=7&period=range&date=last30&disableLink=1&widget=1

Do you see any error in browser console or server error log?

I have an error that I can see in Firebug:

@vincent3569 is the plugin Annotations enabled in your Piwik? This may be the issue, as it seems Piwik won't work well if that plugin is disabled (as it is referenced from plugins/CoreHome/javascripts/dataTable.js)

Hi @mattab

in fact, Annotations plugin wasn't enabled.
I anable it, but nothing happen and the widgetized reports - Visits Over Time - still doesn't work.
and to be more complete, these reports are not working:
-visitors in real time
-visitor profile
-visitor log

in error_log, for most of not working reports, I can see this error:

[18-Sep-2017 06:53:56 UTC] Error in Piwik: SQLSTATE[42S22]: Column not found: 1054 Unknown column 'log_action_event_category.type' in 'field list'

This will be fixed with 3.1.1. In the meantime try activating the Events plugin.

I don't know what is fixed in 3.1.1 but the report "Visits Over Time" still need the plugin Annotations to be activated to work.

Just tried to reproduce, but Visits Over Time works with disabled Annotations plugin. If anyone is having issues with disabled Annotations plugin please open a new issue.