Shopify buy button does not show on the front end

Hello all
I am using the Shopstar theme and I have recently subscribed to the shopify lite buy button. I am not a coder just a layman so I guess I am making some mistakes and would be grateful for some help ??
I have copy pasted the embed code in my post in the text editor and while the button shows up on the visual editor as a tiny image it does not show up on the front end.
Can anyone help please?
P.S. I tried changing the theme, deactivating all the plugins but nothing seems to help.
Thank you
Regards
Nayna