For card subscriptions, you can use a provider Shopify supports for subscription contracts, which in practice means Shopify Payments, or a connected Adyen account through the app. The customer pays the first order in your normal Shopify checkout. Shopify charges renewals on cards it saved, while the app charges Adyen card renewals through your connected Adyen account. If the shop has neither option, the renewal cannot run and the billing attempt reports Shopify Payments (or another payment provider for subscriptions) is not enabled on this shop.
iDEAL, Wero and Bancontact are the exception, because Shopify cannot save them for a later charge. The first order is paid through your own Mollie account, that payment creates a SEPA Direct Debit mandate, and every renewal is collected by direct debit against it. BLIK is another exception: Shopify cannot save it, so the app collects renewals through your Tpay account. Three things are needed: Mollie live in your checkout, Mollie connected in the app, and the Local payment checkout (Mollie) theme app block, because Shopify hides those methods when the cart holds a subscription. "How subscription billing works" explains both side by side.
Stuck on any of this? Open the chat in the bottom right corner of the app and we will help you set it up.