cplusit Hi
Joomla 4 removed this system template so no need to load this css file, you can open file:
/templates//ja_aiga/tpls/blocks/head.php
Look for this code:
<?php
// SYSTEM CSS
$this->addStyleSheet(JUri::base(true) . '/templates/system/css/system.css');
?>
change it to:
if (version_compare(JVERSION, '4.0', 'lt')) {
// SYSTEM CSS
$this->addStyleSheet(JURI::base(true) . '/templates/system/css/system.css');
}