Hi All, i am facing this issue in my sandbox for one of the employee and there is no issue in production

I would double check that their employee record in sandbox has access and if they have a role that is allowed to access sandbox. If you search help, there's plenty of topics on on it.

thanks, i have checked and tried all but still same issue

Is SAML turned on for that role in SB?

how to enable that SAML?

There is a permission under Set Up for SAML, check to make sure that role does not have that permission. We use it and I have seen that message a few times, I just have to send them the link to redo the SSO login with our Microsoft tenant

I guess the question is do you use SAML for your production env? If so, as Todd mentioned you might just need to reimport your IDP file to Sandbox. Or if you don't use SAML - make sure that (again as Todd mentioned) that when you go into Edit on that role in Sandbox, that under Set Up / Enable SAML it is not set