It seems that you are having some issues in order to control the cable box attached to your Slingbox while using the SlingPlayer for Android Mobile devices.
First, I recommend you to test the connection from your computer. This test will allow you to determine if the Slingbox is working in a proper way or not. If you can change channels using the application through www.slingbox.com, I recommend you to uninstall the SlingPlayer for Android Mobile devices and reinstall it one more time.
If you are not able to, I encourage you to check the following links in order to verify if the IR Blasters are working fine:
Let us know how it works for you.