Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/ef4e1416a9ef0d100728ee56eb0e6d79.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563