For this Error:


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.  Go to Settings > Selling > Image Options 


2.  Change Minimum Size Large AND Minimum Size Medium to 500 and Save Settings


3.  Bulk upload action=edit with the affected guids and their media1-10 make sure to check Import Media URLs


4.  Retry Channel Relist