Hello,

The issue you are facing can be due to a several reasons:
- Missing required Windows components;
- Connection to the database may not be established properly (make sure all connection strings are correct in ConnectionStrings.config and all services and database running);
- IIS application might be configured incorrectly;

In order to resolve the error, please follow this deployment procedure. If necessary try redeploying new site and application pool in IIS.
 

Hello Alston, most likely when you get 404 trying to log in after successfully loaded login page, you forgot to enable all .NET Framework 3.5 and .NET Framework 4.8 features in Windows Features window according to the installation manual:

This is very common installation error.

To fix it please follow the manual: https://academy.creatio.com/docs/8.x/setup-and-administration/on-site-deployment/application-server-on-windows/enable-required-windows-components#title-252-2 
 

Dmitriy Gamora,

Thank you for the explanation. My issue is resolved and I am able to login.