Not able to change channels via web site channel listings

I sign into Comcast channel listings via my MacBook.  I was always able to change channels.  I no longer have the abiltiy to do that.  When I click on Watch on TV...it says No compatible cable boxes found!!  How is that?  I can change channels via my iPad, but no longer frim my MacBook.

I called Tech.  They said they would reset my account.   And still no ability to change.  This was working fine until two weeks ago.

Very frustrating!!!