If your onscreen remote is not working and you already verified that the remote is the correct one, have a look at the following article for the IR Emitter placement on your cable box:
If you have the IR Emitter correctly placed, have a look at the following article for testing the IR Emitter to make sure they are functioning properly:
If you find that the IR Emitters are no longer working, you can get a replacement IR Emitter here:
Hope this helps!!!
Sling Media Moderation Team