From the beginning of June eBay will block non-mobile friendly listings.
To update the template for your ads, follow the steps below:
1. Enter the eBay configuration section under Sales Channels >> Ebay;
2. Enter the Configurations >> Templates section;
3. In the model you are using, click on "Templates responsive";
4. Finally, click "Save Settings" at the bottom of the page.
This will generate a valid template for eBay. Then you can customize the template by entering the items you want.
The change will be visible on mobile devices with the subsequent listings updates.