i Wanted to post a response that may help some others. I was having trouble getting sling player to work on a Windows 10 machine while traveling. Same network my IOS devices would work fine.
Another post mentioned an update Microsoft sent through "broke" the media link that the sling player uses. Good news another update partially fixed it. The update that you are looking for is kb4015438
My machine had tried to install this in the usual fashion but failed multiple times. The fix for me was to directly download it and install it from my hard drive.
i found that it fixed the web player off a browser but not the desktop player.
Don;t loose faith in a company like sling because an operating system at times does not like to play nice. Look at it as an opportunity to learn more about your system and to make you more self sufficient in the future.