This post is covering two things really Diane - the first issue is related to themes and you’ll probably get a better response in the Themes forum. The simple answer from someone who is not a theme developer is that different themes are coded to do different things and Boost is designed to be used without blocks in order to free up more screen space for users who want to focus on the site content (see https://moodle.com/news/boost-online-learning-fresh-new-user-experience-moodle-3-2/). If you are going to ask in the Themes forum though, please don’t create a duplicate post saying the same thing, just refer people back to this one.
The second issue is about why blocks don’t appear in the “Add Block” list. That functionality is not dependent on your theme, so if blocks aren’t appearing in that list, it’s likely to be related to one of two things:
- Blocks are designed to appear in certain contexts. Some blocks are coded to not allow multiple instances, or are restricted about where they can appear. So for example, you can add as many HTML blocks to a course page as you wish, but only one calendar block - that’s because it doesn’t make sense to have more than one calendar block in a course. And you can’t add a Flickr block anywhere other than a Tag page. So if you’re adding a block to a context that it’s not designed to be added to, it won’t appear in the list.
- If an installed block is hidden globally, it won’t appear in the “Add Block” list anywhere. See https://docs.moodle.org/35/en/Managing_blocks