unfortunately, it happens sometimes that Microsoft Installer is not able to uninstall some application. Please, use attached utility which removes all Kerio Outlook Connector’s data related to Windows Installer from MS Windows. Then, you will be able to install a new version. To do so, please run the ktuninstaller utility with attached code from command line. It should solve your issue.
ktuninstaller 49075E40-1756-4E55-AEE7-50582D65CCF9