Well you claim your new products do not have (or a wrong) item_group_id in the product feed.
With just the debug.log I cannot check this for myself. You need to check one of your recently added products, a variable product, and see how that one looks in your product feed and it it has an item_group_id or not. When you have only added new simple products to your store than it makes sense as those do not need an item_group_id at all.
In your last reply however you state a different problem about Google complaining products are missing a google_product_category. That is an issue which is not related to item_group_id’s. When I check your XML feed it indeed shows only two products having the google_product_category filled. I therefor checked your category mappings and came across two strange mappings:
This mapping is missing:
[57] => Array
(
[rowCount] => 57
[categoryId] => 57
[criteria] => Skydd
[map_to_category] =>
)
But the one causing issues I think is:
[] => Array
(
[rowCount] =>
[categoryId] =>
[criteria] =>
[map_to_category] =>
)
I have no clue how that ended up there but it is an empty mapping which could be causing problems. I am not sure how this looks in your category mapping interface but could you delete it?
Best
Eva