Page rerun, refresh after user interaction

Using Streamlit
,
1

I am creating a single page st app with login and logout capabilities.
I am using state to check whether a user is authenticated.
When the page loads, all is well. Login form appears
Creds are inputted and then checked against db.
If session_state[‘authenticator’] ==True then other components appear as well as a Logout button.
The problem was that the login form stayed there unless I clicked on Login again (!).
When I clicked on Logout, the other components disappeared, Logout stayed but Login didn’t reappear. When I clicked Logout again then the logout button disappeared and login form appeared.

To solve these problems I used st.rerun() so that the page was re-rendered.
I thought that every time someone clicks on a button or updates a text input etc. the script would re-run anyway. Am I missing something? How is script re-run and page refresh works with streamlit?
I am attaching a redacted version of the code:

import streamlit as st

def verify_creds(email,password):
    results = [{"email": "j.j@a.a", "password": "1234"}] #querying the db for records with given email.
    results = list(results)
    if len(results) > 1:
        st.warning("Multiple users found with the same email and password. Please contact support.")
        st.session_state['authentication_status'] = False
    elif len(results) == 1:
        user = results[0]
        if user["password"] == password:
            st.session_state['authentication_status'] = True
            st.success("Logged in")
            #st.rerun()
        else:
            st.session_state['authentication_status'] = False
            st.warning("Incorrect password")
    else:
        st.session_state['authentication_status'] = False
        st.warning("User not found")
    return 0


if 'authentication_status' not in st.session_state:
    st.session_state['authentication_status'] = None

if not st.session_state['authentication_status']:
    login_form = st.form('Login')
    email = login_form.text_input('Email').lower()
    st.session_state['email'] = email
    password = login_form.text_input('Password', type='password')
    if login_form.form_submit_button('Login'):
        verify_creds(email,password)

if st.session_state['authentication_status']:
    if st.button("Logout"):
        st.session_state['authentication_status'] = False
        st.success("Logged out")
        #st.rerun()
    else:
        st.write('You are seeing the logged in "version" of the app.')