A non partner/affilaite doesn’t/can’t have subscribers
So I’m not sure what you are expecting here?
For example https://www.twitch.tv/barrycarlyonbot is not an affiliate or partner, and doesn’t have a sub button. So would get this error
and https://twitch.tv/cohhcarnage as a parnter, does have a sub button won’t get this error and subscribers are returned.