I have been having the same problem for at least a couple of weeks. Here is the message I've been getting:
Unsupported Configuration
Some content on XFINITYTV.com is not available for viewing with your current configuration. To view
this video using Internet Explorer 10 and Windows please:
If you are viewing this site in Windows 8 Modern Mode, please re-open the page in Desktop Mode.
where Flash is supported.
If you are already in Desktop Mode, then you may need to download and install the latest Adobe
Flash plug-in.
1. How to Install Current Version of Flash.
I have tried everything suggested. When I try to update Flash, I am told I have the most up to date version. I have Windows 8.