YES!! same issue started last Nov/Dec time frame. Desktop player will not work on windows, just use it now to config the box. Have to use browser to view which sucks, poor quality. The iphone app and android app seem to still work, maybe because I paid for them.
I few years ago I found another product out there that was similar to slingbox, can't recall what it was but it may have been volcano or something like that, will need to search for another product. Kodi/TMVC also work but can have poor video quality.
Just very frustrated with sling box and will not recommend it to anybody, I've have 2 now the slingplayer classic which still works and the 350, my last slingboxes will not buy another.
There have been recent changes done to the way you watch and the way to reconfigure. Slingplayer for desktop application is only used for reconfiguration. In order to stream your Slingbox, you would need to go through Newwatch.Slingbox.com. Below are some helpful links:
Sling Media Support Team