Missing variations; not all variations are imported; products are imported as simple products

First, please make sure that you have set the plugin to import all of the variations (or some variations, at least).

Then, you have to make sure that you are importing the right product, that has all the variations.

So, when using Advanced Search: you will have to make sure that the product title does not contain any sizes or colours.

When using CSV Bulk Import: you will have to make sure that you are selecting the right ASIN code, which can be found in the product description (without clicking on other variation).

 

There are some products which are not treated like variations by Amazon and will be imported as simple ones.