If anyone's found that the Genius Mixes have disappeared recently it's seems many are having a similar issue,I can't see a solution at present and it's not platform specific. I'm assuming Genius Mixes is an Apple push service so the problem is at their end.
Best not to update Genius until it's fixed.
I think all the processing is done on their servers.
Well if anyone lost their Genius Mixes they're back.