Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/8d8a7c4a5db69cfc206e3e2c1625f2a3.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563