Two weeks "0 visits"... recalculation possible? (1 reply)

Hey there,
currently there are some troubles using PIWIK. One of theese is as following:

I have an page with about 100 users per day or more.
But if I use the Weekly Graph-View, two weeks have "0 visitors", that isn't correct.

Look at the Screenshot.


1. WHAT could be the Problem?
2. HOW could I may fix this?

Any help is welcome :)

Regards, Oli