Hi Andi,
According to your description, I’d like to confirm if you cannot see the Office installation page as the screenshot shows:
If yes, firstly, please check if you have assigned license to your account. Here are the detailed steps:
a. Sign in to your Office 365 portal > Click Add users, reset passwords, and more under Users & groups.
b. Select the user name > Click the edit icon which is like a pencil.
c. In the licenses section, check if the Office 365 Small Business Subscription has been assigned.
3. In addition, I'd like to confirm if other users who have Office 365 Small Business Subscription license can download Office 2013.
If you have the correct license and still cannot download Office 2013, please feel free to let me know, and we will take a further action to solve the issue.
Thanks,
Tracey Wang