Amazon MCF by ByteStand

Since the implementation of the latest update (known as FLEX, launched May 2024) our store has been broken - orders not being filled automatically, orders being marked as rejected in Shopify but actually processed in Amazon leading to duplicate orders, and our non-Amazon fulfilled orders no longer being fulfilled automatically. Staff I interacted with seemed nice and tried to be helpful, but in the end it's still broken and the result was "this is Shopify's fault, not ours, so nothing we can do about it. If you're a simple store shipping in one region and only using Amazon for fulfillment, then this may work for you. But if your business is slightly more complex, sells products in multiple countries using multiple third parties for fulfillment, then this product in its current state will not meet your needs and may interrupt the non-Amazon automations you have. We're exploring other options.

Used this app for a while. Occasionally it wouldn't allow customers to complete their purchase claiming that we didn't ship to the UK. Approx 2% of orders affected. Shopify adamant problem isn't with them. Tried to get Bytestand to look into the problem but after hearing nothing on the subject have given up. Voting with our feet and moving to another app which also offer inventory synchronization.