Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/d76a6a23ff073b5945da24e8c90a0a6c.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563