First, be sure to click “enable breadcrumbs” in the >internal links section under the Yoast SEO settings.
Second, if its hidden behind another element such as the sidebar, its probably a CSS issue. Try adding something like this to your style sheet:
.sidebar {
position: relative;
z-index: 1;
}
.breadcrumbs {
position: relative;
z-index: 2;
}