Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/d3c7b11d4fc38d5de4f142565f3106b4.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563