If you add a Mermaid chart in a set of tabs, it will not render unless it happens to be on the first tab. This can be reproduced with plain Bootstrap tabs as well: https://jsfiddle.net/sarahg/4gwpbyej/13/ Couple of related posts with potential workarounds: - https://github.com/mermaid-js/mermaid/issues/444 (re-initialize mermaid when you click a tab) - https://github.com/squidfunk/mkdocs-material/issues/3377 (write your own mermaid loader)