Serach function on filterable grid not working

Hey, im a post grid pro user and the load more function and the search function for the filterable grid on my website ist not working. See https://cphp-berlin.de/test/ for examples. I get the error

Uncaught ReferenceError: post_grid_ajax is not defined
at HTMLFormElement.<anonymous> (post-grid-shortcode-scripts.js?ver=6.8.2:38:18)
at HTMLDocument.dispatch (jquery.min.js?ver=3.7.1:2:40035)
at HTMLDocument.<anonymous> (jquery.min.js?ver=3.7.1:2:38006)

in the console, every time i try to search something.

Thanks in advance and best regards
Lorenz