Block isn't showing up live site

I added a Categories block to my Default page but it's not showing on any of the pages. I added it next to the Main Content block.I cleared template cache etc.

Make sure your settings for the block actually fetch data. Empty block data will not show the block.

It's a pre-defined block. It has dropdown vertical as the template, full tree as filling and root level as parent category. Is there something else I need to do to get it to fetch data?

You might want to look at the store in “customization mode” and hover over the area you expect the block to be displayed and then look at the templates used and see if the block is listed.

I don't see it on any of them

Hmm ok it is actually showing up on pages that don't have their own tabs in Design > Blocks. So I need to manually add this block to each of those for it to appear I guess?