After one of the latest WordPress automatic updates my portfolio categories stopped working properly. It is hard to say when exactly, as I’ve only noticed it recently, while it could’ve been present for at least 6-8 months.
Please, update the theme to the latest version 6.1.4. Then, go to Appearance -> Install plugins and update the core plugin also.
After that, go to Settings -> Permalinks and resave them. If the problem remains, let us know so we can investigate it further.