Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/83c9154faf5d3b36e1386639c5fb229d.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563