I have setup a guest sign up block that should display on this page, but i can't see it, even when i am logged off or visit the site on a private browser tab.

Can you see it when you visit it? The form should be right where i have highlighted with a yellow marker

It's on the page, but it's hidden via CSS because there's nothing to show.

Does it contain any content?

No, i thought it would just show the block to sign up?
Do i need a sign up form html or should it just have text in the WYSIWYG field?

Ok @Daniel F i got it!

Its strange that you need to add content to the title and the text field for this to show, even if you just want the sign up form.
Also the text field shows up as title, and the title is in tiny grey font. Not quite as intuitive as i would have imagined, based on how easy the rest of the site is to figure out.

Thanks for the help though!