Total price in Magento and eBay/Amazon/Walmart Orders may differ if you set additional Magento tax settings. Look at the most common cases in the article
Please learn how to make Magento Attributes available for the selection in M2E Pro.
If you’ve just installed M2E Pro to your Magento, you need to go through the Initial Configuration to link Channel accounts
Our Development Team has provided the relevant improvements to make M2E Pro and major Magento update — Multi Source Inventory (MSI) — compatible.
This issue is called double synchronization which often leads to the incorrect product data update on the channel.
You can separate orders placed on sale channels from Magento orders using the order importing.
Check why a product cannot be added to an M2E Pro Listing.