If I change the price of a product, then its no longer possible to use the attribute selector of the translated product. I just tested again on your test site. Same issue.
Languages: English (English )Spanish (Español )German (Deutsch )
Timezone: America/Lima (GMT-05:00)
On this test site, WooCommerce and WPML were not updated.
I updated these plugins now.
Further, edited the product variations on the original product, saved them, and saved the product.
The changes directly showed up on the translated product.
I can currently not replicate the issue. Please give it a another try and let me know the exact steps you are taking in case you can still recreate the issue.
0. Delete all current products, categories, tags etc.
1. import the csv file (you can see the wpmlexample3 csv file in the image library). Result: "Import complete! 2 products imported. 4 variations imported"
2. run the wpml export and import. "We see 6 posts that are imported and need language information." Result: Multilingual Import Complete
3. Visit the store. The product in both languages EN/DE looks fine
4. Edit the price of the EN product, ie. one of the variations and press update
5. Go back to the store and look at the DE product - now the selection field is empty.
And this might be why WPML can not point toward the correct ID.
As I suggested earlier, you should use the same WooCommerce Export method together with WPML & export & Import and avoid manipulating the column values, apart from the text that needs a translation.
See screenshots.
There is one screenshot of your import file that displays that the original product ID is not identical to the parent product ID.