Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/8791c8db6eb1e4649f0759d798033d3a.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563