Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/7d23c09d6f9c8539b285f4d12d5332b2.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563