nagvis upload problem

CMK version:
OS version:

Error message: Failed to execute ajax call. Maybe a network issue or webserver is not available.

HTTP-Status-Code: 500
Time: 1791188100
URL:/monitoring/nagvis/server/core/ajax_handler.php?mod=ManageBackgrounds&act=view&_ajaxid=1791188100

I can’t upload maps/backgrounds and any file, doesn\t matter if it is small 1MB or big, how to fix it ?

Please also provide the information about the used CheckMK version and operating system the CheckMK is running on.
If it is an older version, it is possibly already fixed.