Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/ac2b8f4e9fe73729f45c1ba4a9236160.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563