peterhoejlund

@infinityseeker! Thank you!
This could also be a code in your functions.php removing query strings.
i had:

function _remove_script_version( $src ){
  $parts = explode( '?ver', $src );
  return $parts[0];
}

add_filter( 'script_loader_src', '_remove_script_version', 15, 1 );
add_filter( 'style_loader_src', '_remove_script_version', 15, 1 );

And when i removed that – it all worked again.