Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/a17e0c8c0cc94a3c50588f18344a3e5a.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563