Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/e6cf6feb3d63215f5c8d8f6e496c2fcf.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563