Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/bf6db3e34a716b3e8ddb7f7293a343af.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563