Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/0f1b6d578f0bd6394e5b7573d3d37584.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563