To change the appearance of the brand tile, you need to be the owner of the Brand or an account admin. Even if you are the Owner of a Guideline in that brand, it is only possible to change it if you are the owner or an account admin.

To change the appearance of the Guideline tile, you need to be an owner or editor of that Guideline.

Please contact the owner of the brand or Guideline or reach out to the Frontify Support Team and we can check who the owner is.