Hello Kostas,
We are grateful for your efforts in finding and debugging the issue.
We have tested your site again and modified the slug name and name of the brand attribute, and now your brands are functioning properly.
We have recorded a video of the process for your reference; please view it here: https://www.veed.io/view/43543a37-333b-41e5-b66a-67d3d0e95fe2?sharingWidget=true&panel=share
Best Regards, 8Theme’s Team
