Potentilla heynei Roth should be the correct spelling.
Although the author (Roth) of this name used P. heynii when publishing, he honored this name to "Heyne" instead of "Heyn". Therefore, the spelling used in POWO should be correct.

Translated from this post of @shin-ming_ku :
https://www.facebook.com/groups/iNaturalistTaiwan/posts/1406807803420890/