Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/f87d2e32e8bb6e3a51b5b3667f22a493.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563