Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/dd5ba627fe7825a9935f3aa7c8b63f0b.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563