Open the plugin configure page and enable debugging.
Try to reimport the ebay order and check the plugin log file.
P.S.
Open the order note for old eBay order and remove the first note with ebay order ID. the plugin will import the order again.
Check if nopcommerce task manager works (check your store URL).
This plugin is very popular, many customers use it.
1. Are we able to create new Product Specification Attribute Group via import?
No
2. Are we able to update/add options to Product Specification Attribute?
Specification Attribute and after it Specification Attribute Option
The plugin has several video on our YouTube
https://www.youtube.com/watch?v=YdjGpE3CHvE
1. Check if you configured the purchase event in GTM
2. Create the fake order and check if your order completed page has the tracking code