Failing to install Webcalendar-1.2.7. on strato.de

[xaver-ius]

I copied all extracted files from the zip to a folder webcalendar of my homepage on strato.de
SSL is activated, PHP-Version is set to 8.2.
But if I type my url the only reaction is an error message: _getPhases: could not find '' in _filePhaseMap.
If I type my url with ..../install/index.php nothing happens at all
An old discussion to this error doesn't help me, because it is related to sending of reminders
It seems to be a very basic mistake - but help me please

[xaver-ius]

The Webcalendar-package offered from strato has version 1.9.1.
It uses MariaDB 10.6.
The installation of this package is just a click and an admin-account
But it's not possible to add users!
A error message box with no error code is shown
All other functions seem to work
[Available PHP-versions are 8.0, 8.1. (recommended) and 8.2.] but any of them makes a difference

[xaver-ius]

Installing the offered package and accessing .../install/index.php directly, I got access to the installing script but it couldn't update to the newer DB-version by clicking the button and the script wasn't presented too.

[craigk5n]

Sorry but v1.2.7 did not support PHP8. You'll need to get a more recent version.