If your bundle widgets don't show up anymore, then you most likely created the bundle and then recreated the products or variants in your shop, which changed the product or variant IDs. This means that bundles are configured with old products and variants which don't exist anymore.
To resolve this, just open your bundle in the app, remove the products from the bundle, add them back to it and save the bundle. This will configure the bundle with the new variant and product IDs and everything will be set up correctly again.
If there is an error message displayed in light gray text instead of the bundle widget, then the products from the bundle are not published and visible in your online shop. To resolve this, just publish and activate all products that are included in your bundle.