The subcribestar importer has been broken for like 2 years or so. Yeah it sucks.
The only thing you can do is upload that artist to sites like exhentai.
If I were you, I would be really careful with my SubscribeStar account because of all the "testimonies" other users have posted where their accounts had been banned when they used to import or even without importing content, SubscribeStar have banned their accounts anyway.
They stop the SubscribeStar importer to prevent more people of having their credit cards and future cards block. They implemented a feature that can detect and automatically block people credit cards on their site for using Kemono.
ditto 28430. You can also make a Thread on f95zone.