I have a Schwab account too.  Schwab stopped allowing electronic trading in RVXCF many months ago. 

When I asked, they got back to me saying that the stock had become too volatile to be allowed to be traded electronically (and they got complaints), and asked that I contact their international trading desk to execute trades.  

So the trading halt may be related to that issue...the US traded stock does not show any trading halt on Bloomberg.