This has been happening for a while with one of my sites. It would show no visitors/visits (for the life of the site, then 8, then 5, then 20, then 5, then 1, then 0.)
(We only started using Piwik a month ago - and it’s been great overall.)
Then when I updated to RC2 (we were on the beta channel), my most popular site started showing as no visits/pageviews (when there were a couple thousand of the later.) In some detailed views all the data for date ranges was missing.
I took some screen shots to show the inconsistencies:
[attachment 1453 ScreenShot2013-12-17at11.08.57AM.png]
[attachment 1454 ScreenShot2013-12-17at11.08.28AM.png]
(Note how shiftfocus.ca goes to 0)
By date range for the last 30 days:
[attachment 1455 ScreenShot2013-12-17at11.25.16AM.png]
(note how now LCEEQ.ca, despite a graph showing differently, now shows 0 visits/ 0 page views.)
Furthermore, since I usually use the “last 30 days” date range for normal viewing, when I go look at the site in detail, all the data is missing for browsers, server time access, etc. etc. When I switch the date-range mode to year or month or something else, the data comes back, albeit inconsistently.
The server is currently running 2.0 as of just now and the reports are calculated at most once every hour (though not a cron job.)