That seems to have changed, from what I read:
The fifth referendum was held on June 11, 2017. 97% percent voted for statehood. The 23% voter turnout is as valid as others during their admission process: Wisconsin’s statehood plebiscite had a 17% turnout, Arizona 7%, Hawaii 35%, and Alaska had a 21% turnout.
I seem to recall reading that there was something strange about that referendum, like something happened to affect the numbers or something. But I may be making that up.