During an upgrade, login will not be possible is the Enterprise DSN password is ever changed. It would be good when the box at the bottom that says "Set as system default connection" is checked, then the connection string in the StatInstallInfo.xml should be updated.
From a case:
"I found why the password in the Enterprise DSN section needs to be updated. Basically, there is a StatInstallInfo.xml file that stores the initial connection string when Statistica is first installed. If the DSN password is ever changed, the connection string in the StatInstallInfo.xml is not updated. Then during an upgrade, the upgrade installer re-uses the StatInstallInfo.xml and since the connection string contains the incorrect password login fails after the upgrade."