This message means there’s no information about options which is required to create a Magento order. For example, a Magento configurable product was listed on eBay ignoring variations (as a simple), so eBay order does not have required options and Magento fails to create an order for the item.
Another reason can be the changed option label. For example, the configurable product had the option with name “Color” and with such name it was listed on eBay. Later the name was changed to “Item Color”, so the name of options (variations) on eBay and in Magento are different.
To create an order, you should set up option, go to eBay > Sales in M2E Pro for M1 and eBay Integration > Sales > Order in M2E Pro for M2, click on the necessary order and use Set Options functionality.
Note: Once you make a manual mapping for an option, M2E Pro remembers your choices and all the future orders for this option will be created automatically.