streamlit selectbox on sidebar not working

selectbox on sidebar in streamlit only display the label caption. it doesnt display the drop down menu with the values but if I modify the code and remove ‘sidebar’, it works fine on the main page.

example:

st.sidebar.selectbox('select stock',['APPL', 'GOOG'])

will only display ‘select stock’ on the sidebar without the drop-down menu but

st.selectbox('select stock',['APPL', 'GOOG'])

will work fine on the main page

why is this?