Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/a4c0a9a5fdc88d440c0eae622f6aa03a.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563