Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/8ec6e1f1ee6510dd5dc569f0d33b0932.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563