Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/2af6f9c6971e15a62e3220394cd5d7b7.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563