If you do, have brand assigned, then you need to choose the field name of the brand in the value.
If you don’t and if you are a sole manufacturer, then choose the type as Static and input the name of your Company in the Value field. Then update the feed.
That should add the brand to the feed.
Here’s our youtube playlist.
Follow the instructions in the video for generating the accurate feed.
If you are new or not so well-informed about what Google shopping requires, then you should go through this guide: Guide to Generate WooCommerce Product Feed For Google.