Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/6682b9203827971c49762e2844a5d3b8.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563