In order to get the redo product to work in recharge for subscriptions the merchant will need to add subscription selling plans in their Recharge app.
Inside of the redo product page in recharge ensure that
Redo is available as a one-time product (so it can still be purchased with non subscription products)
Create a subscription plan on the Redo product where the intervals match any subscription that they offer for their other products
Example: if you offer a 30 day subscription a 60 day subscription and a 2 week subscription, create a subscription plan for redo for each of those different options for the Redo product. (the screenshot shows what it looks like for a 2 day subscription and a 4 day subscription)
Be sure to not add a discount for subscribing to Redo.