After upgrading to 2.6.0-b1 my piwik doesnt track any sites anymore.
Also on the dashboard it gives me the following error in NL language:
API returned an error: De datum ‘{’ is geen correct datum bereik. Het moet het volgende formaat hebben: ‘lastN’, ‘previousN’, ‘YYYY-MM-DD,YYYY-MM-DD’. at Range.php:204
The not tracking issue is solved. I had just upgraded the site to https domain. And my tracking piwik site didnt support https lines…
So they where not tracked at that time. Now, since my piwik site is also https, i have tracking enabled again.