Generally, you can upload fonts to both the brands section and the standard font area. Would it be possible to share a screenshot? Also, to confirm, you are logging in with a personal account, not a school or work account, correct?
Hi @David__B, several of us on Discord with a premium account have also raised the same issue in multiple threads. The button still won't show even after performing basic troubleshooting steps, including the ones you mentioned. I looked at Chrome/FF/Edge since I don't use Safari on my PC.
Desktop
Mobile
In the meantime, I noted that the Creative Cloud desktop app would be the way to manage fonts.