This is a very rare error, but has happened to me once before while setting up the local inventory ads for a client.
If your store is closed, ie not open yet. The supplement feed will show error Invalid Store Code. To resolve this, make sure your store is open.
If the above reason is not your case, after some back and forth with Google, they suggest to bulk upload the store information in Google My Business, and this resolved my issue.
Do not use the “Add another business” option.
Below also a checklist for setting up a local inventory feed.
- Set up your accounts
- Enable local inventory ads
- Verify your About page (European countries only)
- Create a local products feed
- Create a local product inventory feed
- Register and submit local feeds.
- Request inventory verification
- Enable local in your Shopping campaigns