No SKU at Orders after Updating WooCommerce and WordPress

Hello,
we are using WordPress, WooCommerce and the premium theme “Impreza”. We have updates WordPress, WooCommerce, Impreza and all plugins. Now the SKU is missing in Dashboard => WooCommerce => Orders.

Before the update, the SKU will be shown on every order directly under the product name. After updating WordPress and WooCommerce there is no SKU. First we thought this is an issue depending on one of the updated plugins or the theme Impreza.

We have created a support ticket at UpSolution (Impreza Theme). We have cloned the website to do some tests with Impreza Support. We have deactivated ALL plugins and Impreza theme itself. We have activated Storefront Shop Theme.

So actually only WordPress, WooCommerce and Storefront are active.
But the issue with non-shown SKUs at Orders is still present.

The support of Impreza theme told me, to contact you with the following words:
Unfortunately, this issue is not related to the Impreza theme, as it replicates with only WordPress, WooCommerce, and Storefront are active.

How to show SKU again, like before updating WordPress / WooCommerce?

Need your help please.

If you need credentials to Admin Dashboard of the cloned site, this is no problem. Tell me if you need.

Kind regards
Bernhard