Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/41cfe3f6ade2b4f172d9f8b1c3469b12.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563