Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/a34f068f1a2de6798a3e26c65e8ed0b8.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563