When you register on our website https://en.dwgfastview.com/ and then you can login the web, the mobile DWG FastView, however if your password containing special characters, you can't login the Windows client. It will give a prompt of Failed to login.
Therefore you are suggested to change your password in your account setting.
Login here https://en.dwgfastview.com/account/SSOAuth?action=preLogin and find:
We are very sorry for the trouble that caused. This bug will be fixed on next version.