So far I’ve managed to import some products to WooCommerce via a CSV file without any problems.
Now after an updating import I noticed that ALL variants are not active:

How can I make all my products active again?
I checked the CSV Docs, there’s not such field to set it on “active”.
In the source code I just found this, and in the DB I also didn’t find anything to set it active with.

/**
 * Controls whether this particular variation will appear greyed-out (inactive) or not (active).
 * Used by extensions to make incompatible variations appear greyed-out, etc.
 * Other possible uses: prevent out-of-stock variations from being selected.
 *
 * @return bool
 */
public function variation_is_active() {
    return apply_filters( 'woocommerce_variation_is_active', true, $this );
}