Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/8f0bb80b1b5561d4f1c94a516f544175.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563