When the backend is installed, it comes  with XML authentication by default. In order continue with XML authentication properly, UsersManagement.xml which is under “C:\ProgramData\IDScan\IDScanEnterprise” needs to be updated with the passwords which meets the complexity requirement. 

Also, Authentication key value needs to be checked if it indicates XML authentication in backendsettings: 

<Setting Value="XML" Key="AuthenticationModule"/> 

IIS should be restarted after XML configuration.