flask run for app.py is not showing login option/tab in the nav-bar/header

I am trying to build a web app with login and signup in the nav-bar/header. When I open the web app using index.html, the login and signup option shows at the top (in nav-bar) but when I do python -m flask run, it never shows that login/signup option. I will attach a snippet of my app.py

First half of app.py

second half of app.py