I upgraded our Piwik installation automatically from 2.4.x to 2.5.0 which was working fine.
After that, we realized that the unique visitor count of the tracked websites restarted at 0 the day of the upgrade in the date range where the upgrade happened. If choosing a custom date range which starts and ends before the upgrade, 0 visitors are shown. If using predefined date ranges (day, week, month), the numbers are still correct, even for dates before the upgrade. Except for the date range the upgrade happened. There is just the count from the update shown.
I attached two PDF documents to explain.
I already changed the archiver to the new version, but without success.
Can anyone reproduce this issue?
Thanks and best regards