Hello satyam pandey,
Based on the error, the account doesn't exist in the tenant. You need to add the user as a guest in the tenant by inviting. Follow the link below to get more information on how to add accounts to tenants by invitation.
https://learn.microsoft.com/en-us/entra/external-id/b2b-quickstart-add-guest-users-portal
Let me know if that works.
Babafemi