For running J!5.1 you must https://fabrikar.com/forums/index.php?wiki/update-from-github/ or include the new file manually https://fabrikar.com/forums/index.php?threads/joomla-5-1-and-fabrik-cannot-find-files-error.54473/post-285151 See also Announcements
Please see our announcement here.
Request URL: https://xxxxxxx/kalender/index.php?option=com_fabrik&view=visualization&format=raw&Itemid=901&id=10
Request Method: POST
Status Code: HTTP/1.1 500 Internal Server Error
Select to use a server's rewrite engine to catch URLs that meet specific conditions and rewrite them as directed. Available for IIS 7 and Apache. Apache users only! Rename htaccess.txt to .htaccess before activating;IIS 7 users only!Rename web.config.txt to web.config and install IIS URL Rewrite Module before activating