After a standard import of products with csv, the brands are not visualized in the imported products. And in the product brand selection there are not even any. I use the old brands through attributes. In attributes the brands are as in the old products that were imported earlier. The same thing happens on other sites where I have imported products. It works on the first site where the product was uploaded directly.
It looks like the brands were not assigned correctly during the CSV import. Since you are using brands as attributes, please check if the attribute values are properly mapped in the CSV file before importing. Also, try re-saving the attributes in products > Attributes.
.
