I don’t see anything about this on Horowitz’s Frontpage site.
There is a message in his Twitter. He is back there and says Twitter claims he was mistakenly suspended.
He posted a sarcastic response about how we could “then get on about killing the jews”. Apparently that got flagged by the twitter auto-search system, and his account was suspended. It was unsuspended later, and does not on its face appear to be more than that.