Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/3b791a865c77a8e7f05a5dff89882b9f.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563