Problems configuring new Adobe Update Server

Hi All,

New update server. 

Windows Server 2019

followed instructions on https://helpx.adobe.com/ca/enterprise/using/setup-ausst.html 

to set up IIS

got to the "To verify extensionless files i went here:"

 http://<server name>/updates/ACC/services/ffc/icons/producticon

and i get an HTTP error 500.19

Detailed Error Information:
Module    CustomErrorModule
Notification    SendResponse
Handler    StaticFile
Error Code    0x800700b7
Config Error    Cannot add duplicate collection entry of type 'mimeMap' with unique key attribute 'fileExtension' set to '.'
Config File    \\?\C:\inetpub\wwwroot\updates\ACC\services\ffc\icons\web.config
Requested URL    http://localhost:80/updates/ACC/services/ffc/icons/productIcon
Physical Path    C:\inetpub\wwwroot\updates\ACC\services\ffc\icons\productIcon
Logon Method    Anonymous
Logon User    Anonymous

any ideas?  

Please let me know if more info is required.

Many thanks,

Michael