Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/aa578d19867a30e8a9a2d0502c79b669.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563