Hi @Fresha Aslam , From AADSTS50020 - User account from identity provider does not exist in tenant documentation, your specific issue would be related to Cause 4 - Guest user wasn't invited.
Because the live.com
(Gmail) user that you're logging in with doesn't belong to the Azure AD tenant. You'll need to sign in with a user that's part of the tenant or have an Admin re-invite you as a Guest user using your Gmail email address. If your user is still part of the tenant, you can also try logging in through a Private Browser to see if that resolves your issue.
Please let me know if you have any questions and I can help you further.
If this answer helps you please mark "Accept Answer" so other users can reference it.
Thank you,
James