We have been using Codisto, now Market Connect, for several years now. It works pretty well for Amazon and eBay.
Walmart was connected about six months ago and has been a nightmare ever since. I have tried working with Codisto support (always helpful) and Walmart support (if you can call it that) and have not been able to narrow down the problem. I might have to try another app for Walmart.
Our products sync ok and update it's the shipping templates that have been the headache. I have followed Walmarts instructions setting up paid shipping and fulfillment centers. I then selected through Codisto which template I want. However, now all my products on Walmart have 2 or 3 templates connected but only use the default free template. I have tried removing manually and through their bulk upload process and either nothing happens or it reverts back after 24 hours.
The main problem is we are losing money on our sales when there is free shipping. Any ideas on how to fix this or a different app to integrate that doesn't have this problem with shipping set ups?