Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/5a34504b9b4f321bb47c6ba82e3eb611.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563