When I try to play Blitz I can't display a board. I was off the site for a while and it worked fine previously before the site was re-designed.
I just checked the blitz site at 1210 GMT and it does not appear to be working at all right now.
I suggest that you keep checking it from time to time and see if it's back.
You could also send a feedback report to admin. It may be a while before it is checked, depending upon what other projects are being worked on.
The feedback link is at the bottom of the page under the support column.