After the initial import JoeLister only updates quantity and pricing.
So (outside of any edits you make) your item within Amazon Inventory will appear much as it did during the initial import to JoeLister.
If you make major changes to a product you will want to re-import the product.
You can re-import using the bulk tools on the top right bulk menu:
Note that if you just want to update the product images there is another tool called "Update Images":
Refresh Inventory After
After using these tools refresh inventory using the button on the top left of the Amazon Inventory page: