Qlik Sense Server Upgrade Fails with "An Error Occurred", missing Repository Database Service

If you upgrade Qlik Sense Server and it fails, the initial error message you receive can be very generic, for example

An error has occurred
For detailed information see the log file

If, after the upgrade fails, you see that there is no longer any Qlik Sense Repository Database present in the services window, this means that the database password validation did not complete and a partial rollback has occurred. This has removed the database software, but it has not removed the database itself.

NOTE: A reboot of the server will occasionally cause this service to re-appear, as sometimes there are just server issues.

The database password is normally password is checked before the upgrade process begins, but under some circumstances, such as the database service being stopped, this check does not occur. Once the new version of the database software is installed it will attempt to open the database as part of the install verification process and will fail. This then prompts a rollback of the database software and removing the new version, unfortunately it does not put back the old version of the database software.

In this case the only solution is to uninstall and then reinstall Qlik Sense as without the database software Qlik Sense will not function.

When you uninstall Qlik Sense you will be asked if you wish to remove the certificates and database, do not do this, if you remove the database and certificates you will need to reconfigure and set up Qlik Sense.

Once Qlik Sense is uninstalled, you can proceed to install the desired upgraded version of Qlik Sense, the installer will detect the existing database and request the password, if it is from an earlier version the installer will make the necessary changes as part of the installation process.