Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/5faf0b38a12d0e7b5e997b8d21c0987a.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563