Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/7bb3990357fc46d316b2e7b5d9e34d3a.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563