Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/f7f0c67f3dc59ba19b5455fa3fa00eed.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563