eBay Error 21919137: Buyers love large photos that clearly show the item, so please upload high-resolution photos that are at least 500 pixels on the longest side.

For this Error:

eBay Error 21919137: Buyers love large photos that clearly show the item, so please upload high-resolution photos that are at least 500 pixels on the longest side.  

The Solution is:

1.  Identify impacted item(s) and find them under the Products tab.

2.  On the Single Product Editor page navigate to the Media section and remove and replace the small images.

3.  Retry relist on eBay.

Note: Images can also be updated using a bulk file with columns action=edit, guid, media1, media2, etc.