Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/d2bf7f7785f370db7aa7873c1c1f0ea5.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563