Session_state won't work in mupli page app

I have multi page app
In the main page I have a user input to save the username is session state, after I go to second page and I need to use the session state usernameā€¦for some reason the session state variable is empty?!

Any information associated to a key in session state that is also used for widget will get deleted when the widget disappears. (This also applies if you assign the same key to a different widget in a different page.)

If you want something to persist across pages, sign it to a key not used for any widget. (Otherwise, you have to copy each key you want to maintain at the top of every page :
st.session_state.my_key =st.session_state.my_key

If that doesnā€™t help, please share your code so we can see what problem you are having.