Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/2c7c69065c501e19e7f9fee7a145b9a4.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563