I use Yoast breadcrumbs from Yoast SEO plugin could that effect the bbpress breadcrumbs
if it checked in the internal links settings
if so to display the bbpress breadcrumbs uncheck it or use this in functions.php in a child theme
remove_filter( 'bbp_get_breadcrumb', '__return_false' );
If you arrived here from a search for “bbpress breadcrumbs missing” like I did…
turn off Yoast’s breadcrumbs at:
YESSSSS!!!!, it worked!!, It was driving me crazy!! Thank you Jay Holtslander!!