Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/a6c3444ba1a6b3f5732301bc56963df4.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563