Anyone have experience with Austrocactus? I ordered some from Mesa Garden. Specifically

Austrocactus dusenii (71.37) JN940 Gan Gan, Chubut 970m, yellow centrals.

I picked that one because it seemed to be furthest south and not at sea level. I soaked the seeds in water for 24 hrs before sowing. About half of the seeds sank while soaking so I thought maybe I'd get about 5 seedlings. One of the seeds popped out a radicle while soaking. However, so far all the other kinds of cacti seeds I ordered have sprouted, even one Sclerocactus, but none of the Austrocactus have sprouted. Any suggestions?