There are two possible scenarios for a "sold out" state, one is the correct genuine behaviour of a sold out bundle and the other is an error in the bundles configuration -normally caused by app conflicts, markets or locations based settings.
Correct Sold Out State:
If your bundle product page displays this specific error message in red: "This bundle is sold out"
This means the bundle is genuinely out of stock because required products for a step aren't available. This is expected behavior.
Incorrect Sold Out State:
Your bundle shows as "Sold Out" on collection and search pages, and the "Add to Cart" button also displays as "Sold Out" on the product page without the red error message. This indicates there's an issue with the bundle's configuration.
Please confirm which of these scenarios your store is currently experiencing. Once confirmed, we’ll assist you in resolving any issues promptly.