Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/5e46b4eb75e9e0d9aa52d7d03277b4a8.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563