MBC Bundles has no subscription engine of its own. It does not bill anyone, set delivery frequencies or manage subscribers. What it does is pass a selling plan from your subscription app through to the cart, so a bundle can be bought on a recurring schedule.

Supported subscription apps are RecurrinGO (recommended), Recharge, Recurpay and Appstle. Everything about the plan itself — frequency, prepaid or pay-as-you-go, subscriber discounts, the customer portal — is configured in that app, not here.

All three, in this order. Missing any one of them means no subscription option on the storefront.

A selling plan on the products. The products in the bundle must carry a selling plan from your subscription app. Create the plan in that app and attach it to the products before you touch the bundle.

Enable integration with subscription apps, on the bundle. Open the bundle, go to the Advanced tab, and tick Enable integration with subscription apps in the Advanced settings card. This is per bundle — it is not a store-wide switch, and it is not in Settings.

Subscription discounts, in Settings. Go to Settings → App settings → Combinations discounts and turn on Subscription discounts. This lets your bundle discount combine with Shopify's subscription discounts store-wide. See "General settings."

Enable integration with subscription apps appears on widget-only bundles and on Physical bundles, in every structure — Classic / Separate products, Product groups, Volume discount and Mix & Match.

It is removed entirely on Shopify-type bundles. If you cannot find the checkbox, check the bundle's type first.

It is also greyed out on the non-primary variant of a running A/B test, along with the other fields the two variants share. Edit the primary variant, or end the test first.

This is the part that catches people out, and it has nothing to do with the bundle's structure.

A subscription selector can only appear where there is a cart line to attach a selling plan to. So the bundle's items have to reach the cart as separate lines.

A Physical bundle set to check out as one combined item shows no subscription selector at all, even with the checkbox ticked, because the cart holds one line for the bundle rather than one line per product. If that is your setup, the fix is a bundle whose items arrive in the cart separately.

The RecurrinGO banner shown next to the checkbox is a promotion, not part of the setup. You can dismiss it.

The Subscription discounts toggle shows the warning "It is not permitted to use the shop without subscribing" while it is on. This is informational only and nothing is wrong.

Each supported app has its own article covering the part that happens inside that app: "RecurrinGO", "Recharge Subscriptions", "Recurpay" and "Appstle Subscriptions integration". The three requirements above are the same whichever one you use.