Rushi
Sign In microflows were removed in the upgrade to version 7 of Mendix (see release notes here: https://docs.mendix.com/releasenotes/desktop-modeler/7.0)
I believe there are plans to bring them back in a future 7 release, but until then, you can use this module https://appstore.home.mendix.com/link/app/66443/Appronto/SignIn-microflow--/-Sign-in-microflow-for-Mx7
Mike