Debug & Update Existing Flask Marketplace application

We have a Flask app which had a UI and feature update recently, the update has left a bug in getting the payment function (stripe payment) to not work in the shopping cart.

The application uses Flask blueprints https://github.com/Anioko/resuable-flask-marketplace. We would like to get the bug hindering successful payment sorted and a few other small issues to deploy the app. The shopping cart has already been developed, same with adding products.

We also would like someone who could be available to enhance it further should we have new requirements, we would discuss and set it up as a separate task.

For this project we want the following:
- Current bug restricting completion of payment by the buyer, cleared to ensure buyer can pay for purchases in the shopping cart.
-Admin should be able to add product variants
-Make the Shipping methods of the seller should be the shown on the order area for the buyer to see.
- Product variants should be optional. It is not compulsory for a product to have a variant.

N/B please don't recommend or suggest that we start the marketplace from scratch. We will not change from Flask to Django or take up another marketplace CMS.