Select one of the programs/channels under "on Now" that is currently live, for example Premier League Years 2019-2020 as shown in the first screenshot below.
You’ll be prompted to sign in (click on the Sign in with Virgin TV UK icon) and the next screen will ask you install the Desktop player which is a windows app so you can watch content on the Sky Sports website. ( If you've already installed the desktop player then just click on the radio box next to "I have already installed the Desktop player".) The app will download and a screen will open so you can watch the program via your laptop browser.
Have you tried using the Sky Sports app on a mobile or tablet? If so did that work?.
Are you signing in by clicking on the Virgin TV UK icon and entering your My Virgin Media details?