Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/59821ffe04645b9a7e6435d64bd0a538.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563