Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/f15932b51eae60d887e0be1fa0e3a1b1.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563