Add HTML or Java

Hi

I am having trouble adding any java or html script. It normally is a simple case of copy and pasting the code into the text tab and it will show up. Every time I do this though it just stays blank and banner that I am looking to add does not show up on the page. The code does remain on the text page but nothing on the visual page after updating. WordPress and themes are up to date so not sure what to try next?

Thanks