I've got 'eBay internal error. The operation was not completed

Probably, you are trying to create eBay listing with variations with Best Offer option. Best Offer option is only used on Fixed Price listings based on Simple products.

To solve this, you just need to set Allow Best Offer to No in the Selling Settings.
For more information, please check: http://docs.m2epro.com/x/PQAJAQ for Magento v1.x versions and http://docs.m2epro.com/x/UwItAQ for Magento v2.x versions


eBay Integration