web.ensureusser method using FBA role works if user is present, otherwise fails

Hi, I'm using SP2010 and I'm having the same issue as described in this link below. Any other resolution on this issue. In powershell EnsureUser is generating this error

I would like to add the rolename to SharePoint Group so I'm using EnsureUser to get the rolename.

Exception calling "EnsureUser" with "1" argument(s): "The specified user c:0-.f|lfbaroleprovider|rolename could not be found."

https://social.msdn.microsoft.com/Forums/vstudio/en-US/f3470f6b-9c15-40a6-8f80-b0cda06c30bd/webensureusser-method-using-fba-role-works-if-user-is-present-otherwise-fails?forum=sharepointdevelopment

Thanks,

JohnWeb