If you have tried setting up Mantine and Tailwind in your project, you would have faced this issue where mantine and tailwind styles end up conflicting with each other. As a result it introduces several unwanted behaviours like your buttons disappearing and only showing when hovered over.
The reason this issue arises is mantine's styles getting overridden by tailwinds. Specifically, tailwinds preflight styles. These preflight styles are applied by default by tailwind in order to normalize styles across across different browsers. As a result mantine's style aren't applied correctly