How to provide access to a dimension to a user

Hi Team,

Hope you are doing well and I would like to know the process to provide access to a particular dimension as user is facing an issue

Steps I performed:

1.Created a group under System

2.Created  a user with OKTA verification 

3.Updated the group to the dimension in Access Group property.

4.Assigned the user to that Group

But user is getting as below

Error: Application access denied because user account is not found or has been misconfigured. Contact your system administrator.

Thanks