Video Data Saver does not work on one app

As a test, I'd install 'NetWorx' on your computer, then try streaming a video from the service on that computer, with the video quality settings on low. NetWorx will let you monitor the bandwidth usage in a live manner. It's got a free 30 day trial, so you wouldn't need to pay for it (it used to be totally free, but they changed it 🙁).

I'd try it both with the VDS off and then on to see if there is any difference. The VDS is supposed to lock the maximum bandwidth down to around 3Mbps when streaming, but a 3GB usage in 90 minutes shows it's not doing that. That's closer to 4.8Mbps, as an average.

I'm not at all familiar with Hallmark Movies Now, as in whether they have an app or you stream directly from their site, but if the former I'd still make sure to set the resolution at the source, as in the website, in order to ensure it's truly streaming in a low resolution.

Lastly, you might want to also use Glasswire on the computer while doing this. Glasswire will show you what apps/processes are using data, and just how much of it. This way you can rule out anything else using data at the same time. It only shows the usage of the device it's installed on, so if another device on your network is using data, it won't show that.

Just some ideas. 

In the end, it's possible that Hallmark Movies Now uses a type of streaming that the VDS just isn't detecting in order to engage, though it's been around for quite a while. If that's the case, hopefully they'll be able to update the VDS so it does.

Edit: I just saw that Hallmark Movies Now is available through Prime. If Prime works well for you, as in the VDS, getting it through them instead may be a viable option. A pain, I know, but just something to keep in mind.