The fine print at the bottom of the page doesn't look promising:
If submitted through this form, it may take a few business days for your CableCARD to be authorized for XFINITY On Demand. If you prefer to use XFINITY On Demand earlier or are still experiencing issues with the application after submitting your information please call Comcast's CableCARD Activation Line (1-877-405-2291) or Comcast Customer Support for assistance.
By providing us with this information, you are consenting to our disclosure of this information to Comcast.
I'd call Comcast directly...