Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/23fe5f38c6394da1c139e9d99b07f582.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563