The zip code you entered is invalid or is not matching your shipping policy.
There are few ways to solve this:
1. Try standardizing your address by doing a zip code look up
eBay uses the USPS database to cross reference addresses to zip code. Go to USPS ZIP Code Lookup and enter your address into their zip code locator. Copy your address exactly as it shows on the USPS website, do not use the plus four part of zip.
2. Use a general shipping method on your eBay business policy
You can use a general shipping method without a specified carrier. Open your business policies page and replace the shipping method with a general one. Choose one of the following shipping services:
Option one
Or, Option two
Once done, re-import the new shipping policy on ExportYourStore's settings and select the new shipping policy. The error from eBay should be gone.