You may run into the following error,
This is not a valid warehouse for the supplier
This means your default warehouse on Listing Mirror does not match the one you have set on Overstock. Here's how you can correct this.
1. Go to your Channel Integration settings, and click the Edit button.
2. On the Advanced tab of your Channel integration settings, you can find the field, "Default warehouse". Change this to match the exact warehouse that is on your Overstock settings. Common errors are not paying attention to the case and spelling.
In your Overstock Supplier Oasis, you can find this here under Account Settings > Warehouse. Click on Update and use the Warehouse Name found here.
3. Overstock errors can take up to 24 hours to go away, so you may have to wait before this error disappears.