Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/0e7f23ad3ae6a25f902c9fb9639f7001.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563