Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/dec869f4c5ce2a72d9e3d3d5c70a6e39.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563