Error while Upgrading from 7.0.3 to 8.0.2

i am getting the below Error while Upgrading from 7.0.3 to 8.0.2

Precondition Failed
The precondition on the request for the URL /install/upgrade.php evaluated to false.
Additionally, a 412 Precondition Failed error was encountered while trying to use an ErrorDocument to handle the request.